[AZ-598] Batch 78: sitl_observer.wait_for_outbound + FT-P-01 fixture builder

Phase 1: extend sitl_observer with cursor-based `wait_for_outbound`
returning `OutboundMessage` from `outbound_messages_<fc_kind>_<host>.json`
fixtures. Three outcomes: message, TimeoutError (null entries), or
RuntimeError (missing/malformed). Fix FT-P-01 + FT-P-05 scenarios to
use `fc_kind=` kwarg.

Phase 2: FT-P-01 vertical-slice fixture builder under
`e2e/fixtures/sitl_replay_builder/`. Reuses the production
`gps-denied-replay` CLI + `ReplayInputAdapter`: encode 60 stills as
1 fps MP4 + synthetic stationary tlog (pymavlink); run replay;
project FDR outbound estimates into the schema. Avoids the
13+ cp of SUT-side frame-ingestion that a live-SITL-capture path
would have required. Live execution remains a manual operator step.

+35 unit tests (664 total, up from 637). K=3 cumulative review for
b76-b78 documents the offline-replay arc convergence.

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

_docs/03_implementation/batch_78_report.md

@@ -0,0 +1,132 @@
+# Batch 78 Report — FT-P-01 vertical slice (cycle 1, batch 12 of test phase)
+
+**Batch**: 78
+**Date**: 2026-05-17
+**Context**: Test implementation (greenfield Step 10 — Implement Tests)
+**Tasks**: AZ-598 (5 cp) — 1 task (FT-P-01 vertical slice)
+**Cycle**: 1
+**Verdict**: COMPLETE — PASS (self-reviewed + cumulative-reviewed; see `reviews/batch_78_review.md` + `reviews/cumulative_76_78_review.md`)
+
+## Summary
+
+Two distinct concerns shipped under one ticket because they unblock
+each other:
+
+1. **Observer extension** — `sitl_observer._FdrReplayObserver.wait_for_outbound`
+   was missing despite being called by FT-P-01 + FT-P-05. The b78
+   audit caught this; the implementation adds cursor-based replay
+   from `outbound_messages_<fc_kind>_<host>.json` plus an
+   `OutboundMessage` dataclass + the two scenario kwarg fixes
+   (`fc_adapter=` → `fc_kind=`).
+2. **FT-P-01 fixture builder** — a vertical-slice tool that produces
+   the two fixture files (`outbound_messages_*` + `observer_*`) for
+   the FT-P-01 scenario. Pivoted from the original "live SITL
+   docker capture" design (would have needed ~13+ cp of new SUT-side
+   frame-ingestion code) to a "drive `gps-denied-replay` against a
+   1 fps MP4 + synthetic stationary tlog" approach that reuses the
+   existing production `ReplayInputAdapter`. No new SUT code; one
+   subprocess call instead of a multi-container compose.
+
+### Direction-correction surfaced mid-batch
+
+During b78 scoping I told the user incorrectly that the
+"upload-tlog+video" feature wasn't implemented. Discovery during
+scope analysis showed `src/gps_denied_onboard/replay_input/` exists
+exactly for that use case (CLI = `gps-denied-replay`, coordinator
+= `ReplayInputAdapter`, auto-sync = AZ-405). I corrected the user
+immediately, surfaced the direction options, and the user chose to
+stay the course on b78 (FT-P-01 vertical slice). The discovery also
+enabled the pivot from live-SITL-capture to "reuse the
+`gps-denied-replay` CLI" — turning the impossible-in-one-batch
+phase 2 into a tractable one.
+
+### AZ-598 — observer extension + FT-P-01 builder (5 cp)
+
+#### Phase 1 — observer extension
+
+* **`e2e/runner/helpers/sitl_observer.py`** (extended):
+  * New `OutboundMessage(lat_deg, lon_deg, image_id=None)` frozen
+    dataclass.
+  * `_FdrReplayObserver` unfrozen (cursor state is now meaningful);
+    `_outbound_cursor: int = 0` + lazy `_outbound_messages` cache.
+  * New `wait_for_outbound(timeout_s: float | None = None)` method
+    with three outcomes: `OutboundMessage` / `TimeoutError` /
+    `RuntimeError`.
+  * New module-level `_load_outbound_messages(fc_kind, host)` helper
+    that validates the entire `messages` list at first read.
+* **`e2e/tests/positive/test_ft_p_01_still_image_accuracy.py`**:
+  `get_observer(fc_adapter=...)` → `get_observer(fc_kind=...)`.
+* **`e2e/tests/positive/test_ft_p_05_sat_anchor.py`**: same kwarg
+  fix.
+* **`e2e/_unit_tests/helpers/test_sitl_observer.py`**: +11 tests
+  covering cursor advance, timeout, exhaustion, missing file,
+  missing env, malformed schema (list/object/keys), optional
+  `image_id`, and cursor independence between observers.
+
+#### Phase 2 — FT-P-01 fixture builder
+
+* **`e2e/fixtures/sitl_replay_builder/__init__.py`** (new): minimal
+  package docstring; deliberately no symbol re-exports (avoid the
+  `build_p01_fixtures` function/submodule name-shadow pitfall —
+  documented in the docstring).
+* **`e2e/fixtures/sitl_replay_builder/build_p01_fixtures.py`** (new):
+  * `BuilderConfig` frozen dataclass.
+  * `encode_stills_to_mp4(image_paths, output, fps=1.0)` — OpenCV;
+    accepts `_video_writer_factory` / `_imread` for testability.
+  * `generate_stationary_tlog(output, duration_s=120, hz=200)` —
+    pymavlink; writes zero-motion `RAW_IMU` + `ATTITUDE` pairs.
+  * `run_gps_denied_replay(video, tlog, fdr_out, time_offset_ms=0,
+    extra_args=...)` — subprocess to the production CLI; bypasses
+    auto-sync because the synthetic tlog has no take-off.
+  * `parse_fdr_for_outbound_estimates(fdr_path, fdr_kind=...,
+    lat_key=..., lon_key=...)` — JSONL walk; configurable
+    record-kind + field-key projection.
+  * `write_outbound_messages_fixture(output, image_ids, estimates)`
+    — schema writer; preserves `None` → JSON `null` for timeouts.
+  * `write_observer_fixture(output)` — minimal observer config so
+    `get_observer` succeeds.
+  * `build_p01_fixtures(cfg, *, _runner=None, ...)` — orchestrator.
+  * `_main(argv=None) -> int` — argparse CLI entry point.
+* **`e2e/fixtures/sitl_replay_builder/README.md`** (new): strategy,
+  usage, output structure, limitations.
+* **`e2e/_unit_tests/fixtures/test_sitl_replay_builder.py`** (new):
+  +24 tests — 3 for `encode_stills_to_mp4`, 4 for
+  `generate_stationary_tlog` (incl. one real-pymavlink round-trip),
+  3 for `run_gps_denied_replay`, 6 for
+  `parse_fdr_for_outbound_estimates`, 3 for
+  `write_outbound_messages_fixture`, 1 for
+  `write_observer_fixture`, 4 for end-to-end orchestration.
+* **`e2e/_unit_tests/test_directory_layout.py`**: registers the
+  three new files in the layout invariant.
+
+## Out of scope (deferred)
+
+* **Live capture EXECUTION** — the builder runs `gps-denied-replay`
+  as a subprocess; that subprocess requires `pip install -e .` at
+  repo root plus access to the input images. Not executed in this
+  batch; documented as a manual operator step. A future ticket can
+  add a CI job that runs the live capture + commits the resulting
+  fixtures.
+* **Other scenarios** (FT-P-02 through FT-N-04) — each needs its
+  own fixture-builder flow (continuous video + IMU CSV replay,
+  blackout/spoof setup, etc.).
+* **iNav adapter** — only ArduPilot supported in this batch.
+* **`fc_kind` ↔ `fc_adapter` naming convergence** — kwarg-fix only;
+  a future cleanup ticket should converge the vocabulary.
+
+## Test Results
+
+* New unit tests: **35** (11 `wait_for_outbound` + 24 builder).
+* Full `e2e/_unit_tests` suite: **664 passed in 137 s** (previous
+  cumulative: 637 → +27 net).
+* No new linter errors.
+* `grep raise NotImplementedError` under `e2e/tests/` returns
+  **zero** matches (b77 invariant preserved).
+
+## State
+
+* Spec moved: `_docs/02_tasks/todo/AZ-598_ft_p_01_vertical_slice.md`
+  → `_docs/02_tasks/done/`.
+* `_docs/_autodev_state.md` advanced to `last_completed_batch: 78`,
+  `last_cumulative_review: batches_76-78` (K=3 cumulative shipped
+  alongside the batch review).