Implement the Level 4 glyph shape lookup function with:
- HAMMING_MAX constant (8) per plan line 1442
- Exact match optimization via binary search fast path
- Frequency tie-breaking for equal Hamming distances
- frequency_table() helper for FREQ_TABLE access
Closes: pdftract-2iur
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
