Verify that the unmapped_glyph_names configuration is properly wired
through to the CMAP entry creation point in Type1 font encoding
differences parsing.
The configuration was already added in bf-4zgpr (commit 7660cfc8). This
bead confirms the wiring is complete:
- DifferencesOverlay stores unmapped_glyph_names as instance state
- Default initialization loads from global UNMAPPED_GLYPH_NAMES set
- Skip check at encoding.rs:227 filters unmapped glyphs before entry creation
- Custom configuration available via with_unmapped_glyph_names() constructor
Acceptance criteria:
- ✅ CMAP entry creation accepts unmapped_glyph_names (via self field)
- ✅ Configuration passes from defaults to entry creation
- ✅ Code compiles without errors
See notes/bf-2nn5x.md for detailed verification.
