[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/02_tasks/done/AZ-598_ft_p_01_vertical_slice.md

@@ -0,0 +1,117 @@
+# FT-P-01 vertical slice: observer wait_for_outbound + SITL capture builder
+
+**Task**: AZ-598_ft_p_01_vertical_slice
+**Complexity**: 5 points
+**Dependencies**: AZ-594, AZ-595, AZ-596, AZ-597
+**Component**: Blackbox Tests / Test Infrastructure (epic AZ-262)
+**Tracker**: AZ-598
+**Epic**: AZ-262 (E-BBT)
+
+## Problem
+
+Batch 78 was scoped as "build the SITL replay fixture builder, vertical
+slice for FT-P-01". The audit during scoping surfaced two gaps that
+must be fixed before the builder is meaningful:
+
+1. FT-P-01 + FT-P-05 call `observer.wait_for_outbound(timeout_s=...)`
+   but `wait_for_outbound` does not exist on `_FdrReplayObserver`.
+   Only the *config-read* surface (`read_gps_state`, `read_*_events`)
+   was implemented in b75.
+2. FT-P-01 + FT-P-05 call `get_observer(fc_adapter=..., host=...)`
+   but the signature is `get_observer(fc_kind, host)`. Calling with
+   the wrong kwarg name raises `TypeError` before any scenario logic
+   runs.
+
+Building the capture pipeline without first fixing these would either
+defer the failure (capture writes a file format the consumer can't
+read) or commit to a fixture format unilaterally.
+
+## Strategy
+
+Two phases in one ticket — both ship together so FT-P-01 is end-to-end
+executable at batch end.
+
+### Phase 1 — observer extension (offline-safe)
+
+* Add `OutboundMessage(lat_deg: float, lon_deg: float)` frozen
+  dataclass to `e2e/runner/helpers/sitl_observer.py`.
+* Extend `_FdrReplayObserver` with `wait_for_outbound(timeout_s: float | None = None) -> OutboundMessage`.
+  * Replay-mode semantics: cursor-based read from
+    `${E2E_SITL_REPLAY_DIR}/outbound_messages_<fc_kind>_<host>.json`.
+  * Each call advances the cursor by one entry.
+  * `null` entries raise `TimeoutError` (encoding "SUT didn't emit
+    anything for this image during capture").
+  * Cursor past list length raises `RuntimeError`.
+  * `timeout_s` accepted for live-mode parity; ignored in replay.
+* Fix call sites: `get_observer(fc_adapter=...)` → `get_observer(fc_kind=...)`.
+
+### Phase 2 — SITL capture builder (FT-P-01)
+
+* New `e2e/fixtures/sitl_replay_builder/build_p01_fixtures.py`:
+  * Stand up the existing `e2e/docker/docker-compose.test.yml` stack.
+  * For each `AD0000NN.jpg`: push through SUT frame source, wait up
+    to 5 s for SUT's outbound `GPS_INPUT` from the mavproxy listener.
+  * Persist `outbound_messages_<fc_kind>_<host>.json` and
+    `observer_<fc_kind>_<host>.json` to `--output` directory.
+* Optional docker compose override `docker-compose.sitl-builder.yml`.
+* Unit tests with mocked docker / mavproxy layer.
+
+## Fixture Format (`outbound_messages_<fc_kind>_<host>.json`)
+
+```json
+{
+  "messages": [
+    {"image_id": "AD000001.jpg", "lat_deg": 48.275292, "lon_deg": 37.385220},
+    null,
+    {"image_id": "AD000003.jpg", "lat_deg": 48.275001, "lon_deg": 37.382922}
+  ]
+}
+```
+
+* `image_id` is optional metadata (diagnostics only).
+* `null` = timeout (no message captured for this image).
+* Entries map 1:1 to scenario `wait_for_outbound` calls in order.
+
+## Acceptance Criteria
+
+**AC-1**: `wait_for_outbound()` returns `OutboundMessage(lat_deg, lon_deg)`
+from the cursor entry.
+
+**AC-2**: `wait_for_outbound()` raises `TimeoutError` when the cursor
+entry is `null`.
+
+**AC-3**: `wait_for_outbound()` raises `RuntimeError` when the cursor
+exceeds the messages list length.
+
+**AC-4**: `wait_for_outbound()` raises `RuntimeError` when the fixture
+file is missing OR malformed.
+
+**AC-5**: FT-P-01 + FT-P-05 use `get_observer(fc_kind=fc_adapter, ...)`.
+
+**AC-6**: `build_p01_fixtures.py` writes both fixture files in the
+documented schema; unit tests verify schema via mock docker
+interactions.
+
+**AC-7**: Full e2e unit-test suite passes (regression gate).
+FT-P-01 + FT-P-05 still skip via `sitl_replay_ready` when env unset.
+
+## Out of Scope
+
+* Live capture EXECUTION — will ask user approval before running
+  (docker-heavy).
+* Other scenarios (FT-P-02 through FT-N-04).
+* iNav adapter for capture — AP first.
+
+## Files Touched
+
+* `e2e/runner/helpers/sitl_observer.py` (extend)
+* `e2e/_unit_tests/helpers/test_sitl_observer.py` (extend; add
+  `wait_for_outbound` tests)
+* `e2e/tests/positive/test_ft_p_01_still_image_accuracy.py` (kwarg fix)
+* `e2e/tests/positive/test_ft_p_05_sat_anchor.py` (kwarg fix)
+* `e2e/fixtures/sitl_replay_builder/__init__.py` (new)
+* `e2e/fixtures/sitl_replay_builder/build_p01_fixtures.py` (new)
+* `e2e/fixtures/sitl_replay_builder/README.md` (new)
+* `e2e/_unit_tests/fixtures/test_sitl_replay_builder.py` (new)
+* `e2e/_unit_tests/test_directory_layout.py` (register new paths)
+* `e2e/docker/docker-compose.sitl-builder.yml` (new, if needed)