Enhanced the `detect_linearization` function to avoid false matches when
extracting keys from the linearization dictionary. Previous implementation
could incorrectly match "/L" within "/Linearized" or "/H" within other keys.
Changes:
- Added loop-based search in extract_number helper to skip substring matches
- Added similar substring-aware logic for /H (hint stream) parsing
- Added new diagnostic codes for /Prev chain error handling
- Added comprehensive verification note
Acceptance criteria PASS:
- Non-linearized files return None
- Valid linearized dict detected correctly
- File size mismatch (incremental update) invalidates linearization
- No /H entry returns None for hint_stream_offset
- Random bytes never panic (proptest)
- Forward scan disabled for linearized files
- INV-8 maintained (no panics on arbitrary input)
Co-Authored-By: Claude Code <noreply@anthropic.com>
