Document the bundled and single-camera MCAP topic contract in docs/mcap_layout.md and link it from the README.
Add scripts/mcap_bundle_validator.py to summarize and validate both bundled /bundle-based MCAPs and single-camera /camera/* MCAPs from Python.
Validate bundled files against bundle-member presence counts and single-camera files against topic/schema expectations plus video/depth/calibration count rules.
