[AZ-599] Batch 79: FT-P-02 Derkachi builder + _common.py extraction

- Add build_p02_fixtures.py: IMU CSV → tlog conversion (RAW_IMU +
  ATTITUDE pairs, centidegrees→radians yaw) and orchestrator that
  runs gps-denied replay against Derkachi MP4 + generated tlog,
  verifying ≥1 record_type="estimate" in the FDR archive.
- Extract run_gps_denied_replay + FDR-parent-dir helpers into
  sitl_replay_builder/_common.py; refactor build_p01_fixtures.py
  to import from _common (b78 tests preserved).
- Add 20 unit tests under e2e/_unit_tests/fixtures/test_sitl_
  replay_builder_p02.py covering AC-1..AC-5; total unit suite
  686/686 passing (regression gate AC-6).
- README updated to document FT-P-01 + FT-P-02 builders.
- Advance autodev state: last_completed_batch=79, current_batch=80;
  prune verbose detail blob.

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/02_tasks/done/AZ-599_ft_p_02_derkachi_builder.md

@@ -0,0 +1,77 @@
+# FT-P-02 Derkachi fixture builder (IMU CSV → tlog, real-motion replay)
+
+**Task**: AZ-599_ft_p_02_derkachi_builder
+**Complexity**: 3 points
+**Dependencies**: AZ-598 (shared `run_gps_denied_replay` helper)
+**Component**: Blackbox Tests / Test Infrastructure (epic AZ-262)
+**Tracker**: AZ-599
+
+## Problem
+
+FT-P-02 (Derkachi continuous-flight drift) needs an offline-replay
+FDR archive so the scenario can compute drift between satellite
+anchors. The b78 FT-P-01 builder doesn't apply directly — FT-P-02
+uses real video + real IMU CSV instead of still images + synthetic
+stationary tlog.
+
+## Strategy
+
+Same overall shape as b78 (drive `gps-denied-replay` against a video
++ tlog pair), with two differences:
+
+1. **Video is already MP4** — skip the OpenCV encoding step.
+2. **IMU is real recorded telemetry** — `data_imu.csv` has 10 Hz
+   `SCALED_IMU2` + `GLOBAL_POSITION_INT` columns. Need a CSV → tlog
+   conversion that packs each row as a `RAW_IMU` + `ATTITUDE`
+   MAVLink pair, with yaw synthesised from `GLOBAL_POSITION_INT.hdg`
+   and roll/pitch=0 (acceptable for fixed-wing cruise).
+
+Output: the SUT's natural FDR archive directory (the b78 schema-
+projection step is dropped because FT-P-02 reads the FDR directly).
+
+## Files Touched
+
+* `e2e/fixtures/sitl_replay_builder/_common.py` (new) — extracts
+  `run_gps_denied_replay` + `write_observer_fixture` from
+  `build_p01_fixtures.py` so b78 + b79 share one implementation.
+* `e2e/fixtures/sitl_replay_builder/build_p01_fixtures.py` (edit)
+  — re-export the moved helpers from `_common.py` for backwards
+  compatibility; b78 tests must still pass unchanged.
+* `e2e/fixtures/sitl_replay_builder/build_p02_fixtures.py` (new) —
+  the FT-P-02 builder.
+* `e2e/fixtures/sitl_replay_builder/README.md` (edit) — document
+  both flows.
+* `e2e/_unit_tests/fixtures/test_sitl_replay_builder_p02.py` (new)
+  — b79 builder tests.
+* `e2e/_unit_tests/test_directory_layout.py` (edit) — register
+  the three new paths.
+
+## Acceptance Criteria
+
+**AC-1**: `convert_imu_csv_to_tlog` parses every row of
+`data_imu.csv` and writes one RAW_IMU + one ATTITUDE pair per row.
+
+**AC-2**: `convert_imu_csv_to_tlog` raises `ValueError` on missing
+required columns OR malformed numeric rows OR empty CSV.
+
+**AC-3**: Heading conversion uses centidegrees → radians
+(`hdg_cdeg * pi / 18000`).
+
+**AC-4**: `build_p02_fixtures` invokes `run_gps_denied_replay` with
+the Derkachi MP4 + the generated tlog; the resulting FDR archive
+contains ≥1 `record_type="estimate"` record (`verify_fdr_has_estimates`
+helper).
+
+**AC-5**: `run_gps_denied_replay` is in `_common.py`; b78 +
+b79 both import it from there; b78 tests still pass.
+
+**AC-6**: Full e2e unit-test suite passes.
+
+## Out of Scope
+
+* Live capture EXECUTION (manual operator step, same as b78).
+* FT-P-04 / FT-P-05 (also use Derkachi but each needs its own
+  builder; deferred).
+* iNav adapter.
+* True SCALED_IMU2 → RAW_IMU unit conversion (pass-through; will
+  re-visit if the SUT's tlog parser rejects).

_docs/03_implementation/batch_79_report.md

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+# Batch 79 Report — FT-P-02 Derkachi fixture builder
+
+**Batch**: 79
+**Date**: 2026-05-17
+**Context**: Test implementation (greenfield Step 10 — Implement Tests)
+**Tasks**: AZ-599 (3 cp) — 1 task (FT-P-02 Derkachi builder + b78 helper extraction)
+**Cycle**: 1
+**Verdict**: COMPLETE — PASS (self-reviewed; see `reviews/batch_79_review.md`)
+
+## Summary
+
+Replicates the b78 vertical-slice pattern for FT-P-02 (Derkachi
+continuous-flight drift). Different from b78 in three ways:
+
+1. **Video is already MP4** — no still-image encoding step.
+2. **IMU is real recorded telemetry** — needs CSV → tlog conversion
+   with real motion data (vs. b78's synthetic stationary tlog).
+3. **Output is the SUT's natural FDR archive directory** — FT-P-02
+   reads it via `fdr_reader.iter_records`, not via the per-call
+   `outbound_messages_*.json` schema b78 ships.
+
+Also extracted `run_gps_denied_replay` + `write_observer_fixture`
+into a shared `_common.py` so both b78 and b79 reference one
+canonical implementation. Future per-scenario builders (FT-P-04
+also uses Derkachi inputs, FT-P-05 needs its own, etc.) will reuse
+the same helpers.
+
+### AZ-599 — FT-P-02 Derkachi builder (3 cp)
+
+* **`e2e/fixtures/sitl_replay_builder/_common.py`** (new): shared
+  `run_gps_denied_replay`, `write_observer_fixture`, `DEFAULT_CLI_BIN`.
+* **`e2e/fixtures/sitl_replay_builder/build_p01_fixtures.py`**
+  (edited): re-imports the moved helpers from `_common.py`; b78
+  tests still pass unchanged.
+* **`e2e/fixtures/sitl_replay_builder/build_p02_fixtures.py`** (new):
+  * `P02BuilderConfig` frozen dataclass.
+  * `convert_imu_csv_to_tlog(csv_path, output_tlog)` — parses
+    `data_imu.csv` rows, packs RAW_IMU + ATTITUDE pairs. Yaw from
+    `GLOBAL_POSITION_INT.hdg` (centidegrees → radians);
+    roll/pitch = 0 (fixed-wing cruise approximation).
+  * `verify_fdr_has_estimates(fdr_path)` — counts
+    `record_type="estimate"` records; raises if zero.
+  * `build_p02_fixtures(cfg, ...)` — orchestrator.
+  * `_main(argv=None)` — argparse CLI.
+* **`e2e/fixtures/sitl_replay_builder/README.md`** (edited): two-
+  builder structure with scenario coverage table; FT-P-01 + FT-P-02
+  per-builder sections with strategy + usage + limitations.
+* **`e2e/_unit_tests/fixtures/test_sitl_replay_builder_p02.py`**
+  (new): +20 tests.
+* **`e2e/_unit_tests/test_directory_layout.py`** (edited): registers
+  the two new modules (`_common.py` + `build_p02_fixtures.py`).
+
+## Out of scope (deferred)
+
+* **Live capture EXECUTION** — same as b78, a manual operator step.
+* **FT-P-04** (Derkachi F2F registration) — also uses Derkachi
+  inputs and could reuse `build_p02_fixtures`. Deferred to a
+  follow-up so this batch ships at 3 cp.
+* **Other scenarios** (FT-P-03 / 05 / 07 / 08 / 10 / 11, FT-N-01..04).
+* **iNav adapter** for FT-P-02.
+* **True SCALED_IMU2 → RAW_IMU unit conversion** — pass-through;
+  re-visit if the SUT's tlog parser rejects.
+* **Aggressive-manoeuvre ATTITUDE synthesis** (roll/pitch ≠ 0) —
+  re-visit if FT-P-04 or other scenarios show fusion drift.
+
+## Test Results
+
+* New unit tests: **20**.
+* Full `e2e/_unit_tests` suite: **686 passed in 123 s** (previous:
+  664 → +22 net = +20 new tests + +2 directory-layout entries).
+* No new linter errors.
+* b78 builder tests (24) still pass after `_common.py` extraction.
+
+## State
+
+* Spec moved: `_docs/02_tasks/todo/AZ-599_ft_p_02_derkachi_builder.md`
+  → `_docs/02_tasks/done/`.
+* `_docs/_autodev_state.md` advanced to `last_completed_batch: 79`.
+* No K=3 cumulative review this batch (next due after b81; the
+  b76-b78 cumulative just shipped one batch ago).
+
+## Incidents
+
+* **Disk-full during regression gate**: the first regression-gate
+  attempt failed with 212 conftest setup errors (all
+  `FileNotFoundError: /var/folders/.../pytest-of-...`). Surfaced
+  to the user with options; user freed space (37 Gi avail after);
+  re-ran the gate and it passed cleanly. Not a code issue.

_docs/03_implementation/reviews/batch_79_review.md

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+# Code Review Report
+
+**Batch**: 79 — AZ-599 (FT-P-02 Derkachi fixture builder + b78 helper extraction)
+**Date**: 2026-05-17
+**Verdict**: PASS
+
+## Findings
+
+(none blocking)
+
+### Non-blocking notes
+
+* **Roll/pitch=0 simplification in synthesised ATTITUDE**: acceptable
+  for the Derkachi fixed-wing cruise data but unrealistic for
+  aggressive manoeuvres. Documented as a Limitation in the README;
+  re-visit if FT-P-04 (Derkachi F2F registration) or other
+  manoeuvre-sensitive scenarios show fusion drift from this gap.
+* **`SCALED_IMU2` → `RAW_IMU` pass-through (no unit conversion)**:
+  the builder passes scaled accelerometer (mg) and gyro (mrad/s)
+  values straight into RAW_IMU fields. Documented as a Limitation;
+  if the SUT's tlog parser rejects, a units conversion pass needs to
+  be added. Surfaced as a follow-up rather than fixed speculatively.
+* **Disk-full incident during regression gate**: not a code issue;
+  surfaced to the user, who freed space, after which the full
+  suite (686 tests) passed cleanly.
+
+## Findings Sweep
+
+### Phase 1 — Context Loading
+
+Read the FT-P-02 scenario to confirm: it (a) skips when
+`sitl_replay_ready` is false; (b) calls
+`fdr_reader.iter_records(fdr_root)` to walk the FDR archive; (c)
+filters for `record_type == "estimate"` and projects into
+`apd.FdrEstimate`. Confirmed FT-P-02 does NOT call
+`wait_for_outbound` (so the b78 schema doesn't apply). Read
+`data_imu.csv` to confirm column names + units (10 Hz; ms
+timestamps; SCALED_IMU2 in mg / mrad/s; GLOBAL_POSITION_INT.hdg
+in centidegrees). Inspected the production
+`replay_input/auto_sync.py` AC-13 contract for required tlog
+message types (RAW_IMU + ATTITUDE) — this drove the choice of
+which messages to pack per CSV row. Verified `pymavlink>=2.4`
+already in `pyproject.toml`. Read the b78
+`build_p01_fixtures.py` to identify the helper extraction
+boundary (`run_gps_denied_replay` + `write_observer_fixture` had
+no FT-P-01-specific code, ideal candidates).
+
+### Phase 2 — Spec Compliance
+
+| AC | Coverage | Status |
+|----|----------|--------|
+| AC-1 (parse every row, one pair per row) | `test_convert_imu_csv_writes_pair_per_row`, `test_convert_imu_csv_real_pymavlink_round_trip` | Covered |
+| AC-2 (ValueError on missing cols / malformed numerics / empty CSV) | `test_convert_imu_csv_empty_raises`, `test_convert_imu_csv_missing_required_column_raises`, `test_convert_imu_csv_malformed_numeric_raises`, `test_convert_imu_csv_missing_file_raises` | Covered (4 distinct error paths) |
+| AC-3 (heading centideg → rad) | `test_hdg_centideg_to_rad` (5 parametric cases: 0, π/2, π, 3π/2, near-2π) | Covered |
+| AC-4 (build_p02 invokes replay + verifies ≥1 estimate) | `test_build_p02_end_to_end_with_mocks`, `test_build_p02_propagates_verify_failure`, `test_verify_fdr_no_estimates_raises`, `test_verify_fdr_counts_estimates`, `test_verify_fdr_tolerates_malformed_lines` | Covered |
+| AC-5 (`_common.py` shared between b78 + b79) | `test_common_module_exports_used_by_b01` + b78 suite (24/24) still passes | Covered |
+| AC-6 (full unit-test suite passes) | 686/686 in 123 s (previous: 664) | Covered |
+
+### Phase 3 — Code Quality
+
+* **Single responsibility**: `convert_imu_csv_to_tlog` parses CSV +
+  packs MAVLink (one cohesive concern: CSV row → tlog pair).
+  `verify_fdr_has_estimates` does one thing. `build_p02_fixtures`
+  is the only orchestrator. Helper extraction into `_common.py`
+  removed duplicate definitions cleanly — no copy-pasted code
+  remains.
+* **No suppressed errors**: every JSON-decode in
+  `verify_fdr_has_estimates` is wrapped in a `try / except
+  json.JSONDecodeError` that explicitly `continue`s with a comment
+  explaining the tolerance (real FDR archives can contain partial
+  writes at the tail). Every CSV parse error wraps in `ValueError`
+  with row context. `subprocess.run` uses `check=True`.
+* **AAA test discipline**: all 20 new tests use
+  `# Arrange / # Act / # Assert`; omitted when redundant.
+* **Comments**: every public function has a docstring documenting
+  contract + raises; no narrating comments in function bodies.
+  The yaw conversion uses a named helper (`_hdg_centideg_to_rad`)
+  rather than an inline magic-formula comment.
+* **Public boundary**: b79 module does NOT import any
+  `src/gps_denied_onboard` symbol (verified by grep). pymavlink
+  imports are deferred to function bodies so the test factory
+  injections don't need the real library available.
+
+### Phase 4 — Security
+
+* No new credentials / secrets / network surfaces.
+* `convert_imu_csv_to_tlog` uses `csv.DictReader` — no `eval`, no
+  shell injection. Numeric fields go through `int(float(s))` so
+  bad input raises ValueError rather than executing arbitrary code.
+* `verify_fdr_has_estimates` uses `json.loads` (safe) and silently
+  ignores malformed lines (documented as tolerance for partial
+  writes; not a security risk because we never act on the data).
+* `subprocess` invocation uses a list-argument `cmd` (no shell
+  injection surface; same pattern as b78).
+
+### Phase 5 — Performance
+
+* `convert_imu_csv_to_tlog` is O(N) over CSV rows; for the Derkachi
+  4,900-row file → ~5 s wall-clock estimate (pymavlink packing is
+  the bottleneck). Bounded by input size; no hidden quadratic
+  behaviour.
+* `verify_fdr_has_estimates` is single-pass O(N) over JSONL lines.
+* `_iter_imu_rows` validates the header once and then streams rows;
+  doesn't materialize the entire CSV in memory until the orchestrator
+  asks for `list(...)` (could be optimized later if Derkachi data
+  ever grows orders of magnitude larger; currently 4,900 rows is
+  trivial).
+
+### Phase 6 — Cross-Task Consistency
+
+* **Builder shape parity with b78**: `BuilderConfig` /
+  `P02BuilderConfig` dataclass; `build_pXX_fixtures(cfg, *, _runner=...,
+  _mavlink_writer_factory=..., _verify_fdr=...)` signature; same
+  underscore-prefixed dependency-injection convention. A future
+  contributor reading both side-by-side will see the same pattern.
+* **`_common.py` extraction validated by both**: b78's existing
+  `test_run_gps_denied_replay_builds_correct_cmd` /
+  `test_run_gps_denied_replay_creates_fdr_parent_dir` /
+  `test_run_gps_denied_replay_passes_extra_args` /
+  `test_write_observer_fixture_schema` tests pass unchanged against
+  the moved implementation. b79 adds
+  `test_common_module_exports_used_by_b01` to lock in the import
+  relationship.
+* **No drift in `observer_<fc_kind>_<host>.json` schema**: same
+  payload structure as b75/b78.
+
+### Phase 7 — Architecture Compliance
+
+* **Module placement**: new files under
+  `e2e/fixtures/sitl_replay_builder/` (existing package from b78);
+  new tests under `e2e/_unit_tests/fixtures/`. All registered in
+  `test_directory_layout.py`.
+* **No `src/gps_denied_onboard` imports**.
+* **No new top-level dependencies** — pymavlink already there from
+  b78/b76; `csv` is stdlib; `math` is stdlib.
+* **`__init__.py` not modified** — the b78 docstring already
+  documents why we don't re-export symbols on the package namespace,
+  and that's still the right choice for b79.
+* **Refactor preserves backwards compatibility**: `build_p01_fixtures`
+  re-imports `run_gps_denied_replay` + `write_observer_fixture`
+  from `_common.py`. Any caller (test or production) doing
+  `bp01.run_gps_denied_replay(...)` still works because the symbol
+  is present in the module namespace via the `from … import …`
+  re-export.
+
+## Test Results
+
+* New unit tests: **20** (5 `convert_imu_csv_to_tlog` + 5
+  `_hdg_centideg_to_rad` parametric + 4 `verify_fdr_has_estimates`
+  + 4 `build_p02_fixtures` end-to-end + 1 export-relationship
+  + 1 missing-file negative).
+* Full `e2e/_unit_tests` suite: **686 passed in 123 s** (previous:
+  664 → +22 net = +20 new + +2 directory-layout entries).
+* No new linter errors (`ReadLints` clean on all touched files).
+* No regression in the b78 builder tests (24/24 still pass after
+  the helper extraction).

_docs/_autodev_state.md

@@ -6,16 +6,16 @@ step: 10
 name: Implement Tests
 status: in_progress
 sub_step:
-  phase: 6
-  name: implement-tasks-sequentially
+  phase: 0
+  name: awaiting-invocation
   detail: ""
 retry_count: 0
 cycle: 1
 tracker: jira
-last_completed_batch: 78
+last_completed_batch: 79
 last_cumulative_review: batches_76-78
-current_batch: 79
-current_batch_tasks: ""
+current_batch: 80
+
 last_step_outcomes:
   step_8: "Code is testable — no changes needed (testability_assessment.md committed; no list-of-changes, no source edits)"
-  step_9: "Already complete — 41 blackbox test tasks (AZ-406..AZ-446) under epic AZ-262 with specs in _docs/02_tasks/todo/ were produced in a prior cycle; AZ-406 test-infrastructure bootstrap also pre-existing. Folder fallback satisfied (todo/ has test tasks, _dependencies_table.md reflects 114 product + 41 test = 155 total). No Step-9 work executed in cycle 1."
+  step_9: "41 blackbox test tasks (AZ-406..AZ-446) under epic AZ-262 in _docs/02_tasks/todo/ pre-existing; AZ-406 test-infra bootstrap pre-existing. Folder fallback satisfied. No Step-9 work executed in cycle 1."