[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>

e2e/fixtures/sitl_replay_builder/README.md

@@ -0,0 +1,77 @@
+# SITL Replay Fixture Builder (AZ-598)
+
+Produces the `outbound_messages_<fc_kind>_<host>.json` +
+`observer_<fc_kind>_<host>.json` fixtures consumed by the b75
+`sitl_observer` module in offline FDR-replay mode (b75/b78).
+
+## Vertical-slice scope (this batch)
+
+Only the FT-P-01 still-image accuracy scenario is supported. Other
+scenarios (FT-P-02 Derkachi continuous flight, FT-N-04 blackout-spoof,
+etc.) need their own capture flows and will land as follow-up tickets.
+
+## Strategy
+
+Rather than spinning up a SITL container, this builder reuses the
+production `gps-denied-replay` CLI + `ReplayInputAdapter`:
+
+1. Encode the 60 `AD0000NN.jpg` still images into a 1 fps MP4.
+2. Generate a synthetic stationary tlog (zero-motion `RAW_IMU` +
+   `ATTITUDE` pairs at 200 Hz) — bypasses the AZ-405 take-off
+   pre-validator without needing real flight data.
+3. Run `gps-denied-replay --video stills.mp4 --tlog stationary.tlog
+   --time-offset-ms 0 --fdr-out fdr.jsonl` (auto-sync bypassed
+   because the synthetic tlog has no take-off signal).
+4. Read `fdr.jsonl`, filter to `kind == outbound_position_estimate`,
+   project each into the `outbound_messages_*` schema.
+5. Write the two fixture JSON files into `--output-dir`.
+
+This avoids needing new SUT-side frame-ingestion code (HTTP endpoint,
+file-watch source, etc.) which would otherwise be required to push
+individual stills to a running SUT container.
+
+## Usage
+
+```bash
+gps-denied-build-p01-fixtures \
+  --input-dir _docs/00_problem/input_data \
+  --output-dir e2e/fixtures/sitl_replay/p01 \
+  --fc-kind ardupilot \
+  --host sitl-host
+```
+
+The output directory will contain:
+
+* `stills.mp4` — the 60 images encoded at 1 fps.
+* `stationary.tlog` — synthetic 120-s zero-motion tlog at 200 Hz.
+* `fdr.jsonl` — the FDR JSONL stream from the replay run.
+* `outbound_messages_ardupilot_sitl-host.json` — the consumed fixture.
+* `observer_ardupilot_sitl-host.json` — the consumed fixture.
+
+To activate the fixtures in a scenario run:
+
+```bash
+E2E_SITL_REPLAY_DIR=e2e/fixtures/sitl_replay/p01 \
+    pytest e2e/tests/positive/test_ft_p_01_still_image_accuracy.py
+```
+
+## Limitations
+
+* The synthetic tlog encodes zero motion — auto-sync MUST be bypassed
+  via `--time-offset-ms 0` (the builder does this automatically).
+* The FDR record `kind` is assumed to be `outbound_position_estimate`
+  — the `--fdr-kind` CLI flag overrides if the actual schema differs.
+* Per-image timeout handling: if the SUT emits fewer outbound estimates
+  than pushed frames, trailing image_ids are written as `null` entries
+  (encoded as TimeoutError on scenario replay).
+* iNav adapter is NOT supported by this batch — only ArduPilot. iNav
+  will land as a follow-up once the AP path is validated end-to-end.
+
+## Testing
+
+Unit tests under `e2e/_unit_tests/fixtures/test_sitl_replay_builder.py`
+mock all external dependencies (OpenCV, pymavlink, subprocess) so the
+test suite runs without a real `gps-denied-replay` install. The actual
+end-to-end run requires the SUT to be installed (`pip install -e .` at
+repo root) and is documented as a manual step until CI infrastructure
+catches up.