docs(pdftract-5f92): add verification note for Type3 font loader

Documents the completed Type3 font loader implementation,
acceptance criteria status, and test coverage.

Verification:
- All 13 unit tests pass
- All acceptance criteria PASS
- Commit ece0442 contains the implementation

notes/pdftract-5f92.md

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+# Verification Note: pdftract-5f92 - Type 3 Font Loader
+
+## Summary
+
+Implemented Type3 font loader in `crates/pdftract-core/src/font/type3.rs` with complete support for:
+- `/CharProcs` (HashMap<Arc<str>, ObjRef> from glyph name to content stream reference)
+- `/FirstChar`, `/LastChar` (character code range)
+- `/Widths` array (advance widths in glyph space)
+- `/FontMatrix` 3x3 transform (default [0.001 0 0 0.001 0 0])
+- `/Resources` (optional resource dictionary for glyph streams)
+- `/Encoding` (code -> glyph name mapping)
+
+## Implementation
+
+**File:** `crates/pdftract-core/src/font/type3.rs`
+
+**Struct:** `Type3Font` with all required fields plus diagnostics vector.
+
+**Methods:**
+- `load(font_dict)` - Main entry point for loading Type3 fonts
+- `advance_for(code)` - Get advance width for a character code (applies FontMatrix transform)
+- `char_proc(glyph_name)` - Get stream reference for a glyph
+- `has_glyph(glyph_name)` - Check if glyph exists
+- `glyph_count()` - Get number of glyphs
+
+## Acceptance Criteria Status
+
+- ✅ **PASS:** Valid Type 3 font loads with all fields populated
+- ✅ **PASS:** `/FontMatrix [0.001 0 0 0.001 0 0]`: advance for code with width 500 -> 0.5 text-units
+- ✅ **PASS:** `/FontMatrix [1 0 0 1 0 0]` (identity): same width 500 -> 500 text-units
+- ✅ **PASS:** Missing `/Widths` defaults to all-zero with diagnostic
+- ✅ **PASS:** Code outside [FirstChar, LastChar] returns advance 0 with no panic
+
+## Test Coverage
+
+13 unit tests covering:
+- `test_type3_load_minimal` - Basic loading with defaults
+- `test_type3_with_char_procs` - CharProcs dictionary parsing
+- `test_advance_for_with_standard_font_matrix` - Standard FontMatrix scaling
+- `test_advance_for_with_identity_font_matrix` - Identity FontMatrix (no scaling)
+- `test_advance_for_out_of_range` - Out-of-range code handling
+- `test_widths_length_mismatch` - Widths validation (pad with zeros)
+- `test_widths_too_long` - Widths validation (truncate)
+- `test_missing_widths` - Default to all-zero with diagnostic
+- `test_missing_char_procs` - Empty char_procs map
+- `test_custom_font_matrix` - Custom FontMatrix values
+- `test_with_resources` - Resources dictionary parsing
+- `test_arbitrary_glyph_names` - Non-AGL glyph name support
+- `test_encoding_parse` - Encoding parsing integration
+
+All tests pass:
+```
+running 13 tests
+test result: ok. 13 passed; 0 failed
+```
+
+## Critical Considerations Handled
+
+- ✅ Advance width calculation: `Widths[C - FirstChar] * FontMatrix[0]`
+- ✅ Widths length mismatch emits `TYPE3_WIDTHS_LENGTH_MISMATCH` diagnostic and clamps/pads
+- ✅ Empty CharProcs treated as zero-glyph font (malformed but handled)
+- ✅ Arbitrary glyph names supported (not assumed to be AGL names)
+- ✅ FontMatrix default [0.001 0 0 0.001 0 0] applied correctly
+- ✅ Resources optional (defaults to None, page resources used downstream)
+
+## Commit
+
+**Commit:** `ece0442` - "feat(pdftract-5f92): implement Type3 font loader"
+
+## Integration
+
+- Exported from `font/mod.rs` as `pub use type3::Type3Font`
+- Classified by `classify_font()` as `FontKind::Type3`
+- Ready for integration with Phase 2.2 resolver chain for encoding resolution