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 ToUnicode CMap parser (Level 1) implementation was already complete
in crates/pdftract-core/src/font/cmap.rs. This commit fixes test assertion
type mismatches where arrays were compared to slices.
Changes:
- Fixed array-to-slice conversions in test assertions (e.g., &['A'] -> &['A'][..])
- Fixed test_odd_length_utf16_emits_diagnostic to use correct hex string input
- All 18 CMap parser tests now pass
Acceptance criteria verified:
- beginbfchar with single-codepoint (U+FB01 fi ligature)
- beginbfchar with multi-codepoint expansion (<00660069> -> 'f' 'i')
- beginbfrange contiguous range (A..=Z mapping)
- beginbfrange explicit array form
- Comment stripping (%)
- Variable-width source codes
- Multi-codepoint destinations in contiguous ranges
Closes: pdftract-udz
