fix(stereo-split): repair bursty container timestamps

[shark0F0497]

Summary

• detect unhealthy MCAP log_time and publish_time independently when CompressedImage.header.stamp is trustworthy
• leave healthy timelines unchanged and skip repair when header timestamps are missing, non-monotonic, or unstable
• rebuild affected video timestamps from header cadence and keep copied topics aligned, including duplicate/backward outer timestamps
• expose repair status, reason, affected axes, and repaired message count in processing metadata and manifests

Verification

• 33/33 stereo-split tests pass
• capture (1).mcap: repaired 8,530 frames; outer gap P50/P99/max changed from 0.219/455.266/2135.695 ms to 16.002/31.996/32.050 ms
• src_15b29652df9cabc04f444695420d4141.mcap: 988 frames; detected as healthy and left unchanged
• session_002.mcap: H.264 input path produced 1,506 stereo frame pairs after skipping 11 pre-IDR frames; 16,687 IMU and 13 serial-number messages were preserved byte-for-byte

Review

• Standards review: no hard violations
• Spec review: no findings