[AZ-698] Multi-flight tlog handling: segment first, pick last flight

Real derkachi.tlog covers 3 takeoffs at the same field but the
uploaded video covers only the last. Original NCC argmax + AZ-405
head-takeoff fallback both biased toward flight 1, violating the
spec's "the last chunk in tlog is relevant" framing.

Patch: pre-NCC flight segmenter partitions the IMU energy stream
into distinct flights (threshold + gap walk); find_aligned_window
restricts NCC search to the last segment; low-confidence fallback
uses that segment's start instead of head-takeoff detection.
AlignedWindow gains flight_count_detected + selected_flight_index
for FDR-visible audit.

7 new unit tests (segmenter shapes + end-to-end multi-flight
pipeline + segmented fallback path). 19 AZ-698 tests pass, 113
in the regression slice. Zero new mypy --strict errors.

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

src/gps_denied_onboard/runtime_root/_replay_branch.py

@@ -271,6 +271,15 @@ def _build_auto_sync_config(config: Config) -> AutoSyncConfig:
         alignment_resample_hz=block.alignment_resample_hz,
         alignment_video_scan_seconds=block.alignment_video_scan_seconds,
         alignment_low_confidence_threshold=block.alignment_low_confidence_threshold,
+        alignment_segment_motion_threshold_g=(
+            block.alignment_segment_motion_threshold_g
+        ),
+        alignment_segment_min_flight_duration_seconds=(
+            block.alignment_segment_min_flight_duration_seconds
+        ),
+        alignment_segment_max_internal_gap_seconds=(
+            block.alignment_segment_max_internal_gap_seconds
+        ),
     )