[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>

tests/unit/test_az401_compose_root_replay.py

@@ -41,6 +41,7 @@ from gps_denied_onboard.components.c8_fc_adapter.tlog_replay_adapter import (
 )
 from gps_denied_onboard.config import (
     Config,
+    ConfigError,
     ReplayAutoSyncConfig,
     ReplayConfig,
     RuntimeConfig,
@@ -733,3 +734,58 @@ def test_compose_root_replay_with_no_calib_path_raises(
         match=r"(camera_calibration_path|CAMERA_CALIBRATION_PATH)",
     ):
         compose_root(config)
+
+
+# ----------------------------------------------------------------------
+# AZ-611 — ReplayConfig.skip_auto_sync_validation schema gate
+
+
+def test_az611_skip_auto_sync_without_manual_offset_rejected_at_init() -> None:
+    """``__post_init__`` refuses ``skip_auto_sync_validation=True`` paired
+    with ``time_offset_ms=None`` — the bypass is only legal once the
+    operator has committed to an explicit manual offset.
+    """
+    # Act / Assert
+    with pytest.raises(
+        ConfigError,
+        match=r"skip_auto_sync_validation=True requires.*time_offset_ms",
+    ):
+        ReplayConfig(
+            video_path="/dev/null/fake.mp4",
+            tlog_path="/dev/null/fake.tlog",
+            output_path="/tmp/replay.jsonl",
+            pace="asap",
+            time_offset_ms=None,
+            skip_auto_sync_validation=True,
+            target_fc_dialect="ardupilot_plane",
+        )
+
+
+def test_az611_skip_auto_sync_with_manual_offset_accepted() -> None:
+    """The legal combination — ``skip_auto_sync_validation=True`` with an
+    explicit ``time_offset_ms`` — constructs cleanly and round-trips
+    both flags onto the frozen dataclass.
+    """
+    # Act
+    cfg = ReplayConfig(
+        video_path="/dev/null/fake.mp4",
+        tlog_path="/dev/null/fake.tlog",
+        output_path="/tmp/replay.jsonl",
+        pace="asap",
+        time_offset_ms=0,
+        skip_auto_sync_validation=True,
+        target_fc_dialect="ardupilot_plane",
+    )
+
+    # Assert
+    assert cfg.skip_auto_sync_validation is True
+    assert cfg.time_offset_ms == 0
+
+
+def test_az611_skip_auto_sync_defaults_to_false() -> None:
+    """Default-constructed ReplayConfig must not opt out of validation."""
+    # Act
+    cfg = ReplayConfig()
+
+    # Assert
+    assert cfg.skip_auto_sync_validation is False