Enhanced all assertion messages in cmap_unmapped_glyphs.rs to follow a consistent pattern:
- What was expected
- What was found
- Why this matters
Modified tests:
- test_cmap_unmapped_glyph_skip: Added detailed messages for unmapped checks, map validation, and lookups
- test_cmap_multiple_mappings_with_unmapped_check: Enhanced mapping verification messages
- test_cmap_range_mapping_with_unmapped_awareness: Improved range expansion and boundary check messages
All 7 tests pass successfully. Assertion messages now provide maximally helpful diagnostics when failures occur.
Verification: notes/bf-18a0w.md
