[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/_unit_tests/test_directory_layout.py

@@ -57,6 +57,9 @@ E2E_ROOT = Path(__file__).resolve().parents[1]
         "runner/helpers/blackout_spoof_evaluator.py",
         "runner/helpers/fc_proxy_runtime.py",
         "runner/helpers/replay_mode.py",
+        "fixtures/sitl_replay_builder/__init__.py",
+        "fixtures/sitl_replay_builder/build_p01_fixtures.py",
+        "fixtures/sitl_replay_builder/README.md",
         "fixtures/mock-suite-sat/Dockerfile",
         "fixtures/mock-suite-sat/app.py",
         "fixtures/mock-suite-sat/requirements.txt",