Implement per-word validation filter for assisted-OCR BrokenVector path.
Changes:
- Add SpanSource::OcrAssisted variant to hybrid.rs
- Add Span::ocr_assisted() helper method
- Implement validate_ocr_with_position_hints() in ocr.rs
- 5pt distance threshold for position validation
- 0.4 confidence cap for rejected words
- Linear scan for nearest-neighbor lookup
- Add unit tests for validation filter
Closes: pdftract-3s2i
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
The --root DIR flag was already fully implemented in the codebase.
All 25 tests pass (12 unit + 13 integration tests).
Acceptance criteria verified:
- Path traversal rejected with -32602
- Absolute paths rejected when --root is set
- HTTPS URLs bypass the check
- Symlink escapes detected via canonicalize
- Startup validation for root directory
Co-Authored-By: Claude Code <noreply@anthropic.com>
