[AZ-611] Add --skip-auto-sync flag to bypass AC-9 validator

Mid-flight fixtures (Derkachi) and stationary-still scenarios
(FT-P-01) have no take-off spike for the IMU detector and produce
false-positive video motion onsets, so the AC-9 frame-window
validator rejects every plausible offset. Add an operator-acknowledged
opt-out: a new ReplayConfig.skip_auto_sync_validation flag that
suppresses validation, paired with a hard requirement that
time_offset_ms also be set (silent-zero guard at both schema and
adapter layers).

Wired through schema -> CLI (--skip-auto-sync) -> composition root
-> ReplayInputAdapter; Derkachi e2e fixture now passes
time_offset_ms=0 + skip_auto_sync=True by default since the synth
tlog and the video share the same t=0 anchor by construction.

5 new unit tests:
  * schema gate rejects skip=True without manual offset
  * schema gate accepts the legal pair
  * default field value is False (default-construction safety)
  * adapter constructor mirrors the schema gate
  * adapter open() bypasses validate_offset_or_fail when flag is set

All 38 unit tests in test_az401 + test_az405 pass on Mac.

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

src/gps_denied_onboard/replay_input/tlog_video_adapter.py

@@ -105,7 +105,16 @@ class ReplayInputAdapter:
       the coordinator's own structured-event mirror.
     - ``pace`` — :class:`ReplayPace` (``ASAP`` or ``REALTIME``).
     - ``manual_time_offset_ms`` — ``None`` triggers auto-sync; an
-      integer bypasses auto-sync entirely (AC-8).
+      integer bypasses auto-sync DETECTION but the AC-9 frame-window
+      validator still runs on the resolved offset (AC-8).
+    - ``skip_auto_sync_validation`` — when ``True``, ALSO skip the
+      AC-9 validator. Only legal in combination with a non-``None``
+      ``manual_time_offset_ms`` (the coordinator refuses both-None
+      to avoid silent-zero offset bugs). Intended for fixtures where
+      neither the IMU take-off detector nor the video motion-onset
+      detector can produce a reliable signal (mid-flight clips,
+      stationary still-image scenarios — see AZ-611). Default
+      ``False``.
     - ``auto_sync_config`` — :class:`AutoSyncConfig` thresholds.
 
     Behaviour:
@@ -127,6 +136,7 @@ class ReplayInputAdapter:
         "_fdr_client",
         "_pace",
         "_manual_time_offset_ms",
+        "_skip_auto_sync_validation",
         "_auto_sync_config",
         "_tlog_source_factory",
         "_video_frames_factory",
@@ -150,6 +160,7 @@ class ReplayInputAdapter:
         pace: ReplayPace,
         manual_time_offset_ms: int | None,
         auto_sync_config: AutoSyncConfig,
+        skip_auto_sync_validation: bool = False,
         tlog_source_factory: Any | None = None,
         video_frames_factory: Any | None = None,
         video_timestamps_factory: Any | None = None,
@@ -172,6 +183,22 @@ class ReplayInputAdapter:
             raise ReplayInputAdapterError(
                 f"pace must be a ReplayPace enum; got {type(pace).__name__}"
             )
+        if not isinstance(skip_auto_sync_validation, bool):
+            raise ReplayInputAdapterError(
+                "skip_auto_sync_validation must be a bool; got "
+                f"{type(skip_auto_sync_validation).__name__}"
+            )
+        if skip_auto_sync_validation and manual_time_offset_ms is None:
+            # Mirror the ReplayConfig.__post_init__ gate. Without a
+            # manual offset there is no operator-acknowledged value
+            # to skip validation against — auto-sync would compute
+            # an offset of unknown quality and the validator that
+            # would catch a bad detection is disabled. Refuse so
+            # this can't silently mask a wrong offset.
+            raise ReplayInputAdapterError(
+                "skip_auto_sync_validation=True requires "
+                "manual_time_offset_ms to be set"
+            )
         self._video_path = video_path
         self._tlog_path = tlog_path
         self._camera_calibration = camera_calibration
@@ -180,6 +207,7 @@ class ReplayInputAdapter:
         self._fdr_client = fdr_client
         self._pace = pace
         self._manual_time_offset_ms = manual_time_offset_ms
+        self._skip_auto_sync_validation = skip_auto_sync_validation
         self._auto_sync_config = auto_sync_config
         self._tlog_source_factory = tlog_source_factory
         self._video_frames_factory = video_frames_factory
@@ -221,21 +249,39 @@ class ReplayInputAdapter:
                 },
             )
 
-        # Step 3 — load video frame timestamps and run AC-9 validator.
+        # Step 3 — load video frame timestamps and run AC-9 validator
+        # unless the operator explicitly opted out via
+        # skip_auto_sync_validation (AZ-611). The opt-out is meant for
+        # mid-flight + stationary fixtures where neither detector can
+        # produce a reliable signal; the constructor already enforced
+        # that the opt-out requires a manual offset.
         video_frame_timestamps_ns = self._load_video_timestamps()
-        result_code = validate_offset_or_fail(
-            resolved_offset_ms,
-            tlog_imu_timestamps_ns,
-            video_frame_timestamps_ns,
-            threshold_pct=self._auto_sync_config.match_threshold_pct,
-            window_ms=self._auto_sync_config.match_window_ms,
-        )
-        if result_code != 0:
-            self._raise_ac8_fail(
-                resolved_offset_ms,
-                len(tlog_imu_timestamps_ns),
-                len(video_frame_timestamps_ns),
+        if self._skip_auto_sync_validation:
+            self._log.info(
+                f"{_LOG_KIND_OPEN_MANUAL}: ac9_validator_skipped "
+                f"(resolved_offset_ms={resolved_offset_ms})",
+                extra={
+                    "kind": _LOG_KIND_OPEN_MANUAL,
+                    "kv": {
+                        "resolved_offset_ms": resolved_offset_ms,
+                        "ac9_validator_skipped": True,
+                    },
+                },
             )
+        else:
+            result_code = validate_offset_or_fail(
+                resolved_offset_ms,
+                tlog_imu_timestamps_ns,
+                video_frame_timestamps_ns,
+                threshold_pct=self._auto_sync_config.match_threshold_pct,
+                window_ms=self._auto_sync_config.match_window_ms,
+            )
+            if result_code != 0:
+                self._raise_ac8_fail(
+                    resolved_offset_ms,
+                    len(tlog_imu_timestamps_ns),
+                    len(video_frame_timestamps_ns),
+                )
 
         # Step 4 — clock strategy (single instance per Invariant 2).
         clock = self._build_clock()