bf-4g7gb: Create unmapped glyph test fixture

Task

Create a PDF test fixture containing glyphs without valid Unicode mappings that trigger the FONT_GLYPH_UNMAPPED diagnostic.

Finding

The fixture already exists at tests/fixtures/encoding/no-mapping.pdf and meets all acceptance criteria.

Acceptance Criteria - ALL MET

✅ Test fixture PDF exists in tests/fixtures/

Location: tests/fixtures/encoding/no-mapping.pdf
Size: 660 bytes
SHA256: b24f88d3add958bfec1d6b134f2cd030cd41bb1932bedbe99405599bd01fa8f0

✅ Fixture contains at least one glyph without a Unicode mapping

Contains three unmapped glyphs: /g001, /g002, /g003
Custom encoding differences array: [0 /g001 /g002 /g003]
No ToUnicode CMap
No standard encoding
Non-AGL glyph names (not in Adobe Glyph List)
Content stream uses byte codes <000102> to reference the three glyphs
Expected extraction: U+FFFD U+FFFD U+FFFD (three replacement characters)

✅ Fixture is documented with expected unmapped glyphs

Documented in tests/fixtures/PROVENANCE.md (line 199-208):

# encoding/no-mapping.pdf
Generated by tests/fixtures/generate_unicode_recovery_fixtures.rs
PDF 1.4, Type1 font with custom glyph names, no ToUnicode CMap, no standard encoding
Level 4 Unicode recovery test fixture (worst case: no encoding fallback)
Content: <20><><EFBFBD> (three U+FFFD replacement characters - glyph names /g001/g002/g003 are not in AGL and cannot be recovered)

Generator code at tests/fixtures/encoding/generate_unicode_recovery_fixtures.rs:68-98 with clear comments:

/// no-mapping.pdf: Custom encoding, no ToUnicode, no standard encoding
/// Tests Level 4 worst-case: No ToUnicode, no AGL match, no fingerprint match

Ground truth file: tests/fixtures/encoding/no-mapping.txt containing <EFBFBD><EFBFBD><EFBFBD> (9 bytes UTF-8)

Additional Verification

FONT_GLYPH_UNMAPPED Diagnostic

Diagnostic code: FONT_GLYPH_UNMAPPED
Definition: crates/pdftract-core/src/diagnostics.rs:17 (DiagCode::FontGlyphUnmapped)

Emission logic: crates/pdftract-core/src/font/resolver.rs:24-26

/// Emit the GLYPH_UNMAPPED diagnostic exactly once per (font, code) miss.

JSON output test: crates/pdftract-core/src/output/json.rs:369-386

assert_eq!(error_json[0].code, "FONT_GLYPH_UNMAPPED");
assert_eq!(error_json[0].severity, "error");

Integration Tests

Encoding recovery test: crates/pdftract-core/tests/encoding_recovery.rs:210-223

#[test]
fn test_no_mapping_fixture() {
    let fixture = Fixture {
        name: "no-mapping".to_string(),
        pdf_path: PathBuf::from(format!("{}/no-mapping.pdf", FIXTURES_DIR)),
        ground_truth_path: PathBuf::from(format!("{}/no-mapping.txt", FIXTURES_DIR)),
    };
    let (_, recovery_rate, _) = test_fixture(&fixture);
    assert!(recovery_rate >= MIN_RECOVERY_RATE, ...);
}

Used throughout codebase by 40+ test and debug files (grepped from codebase)

PDF Structure

%PDF-1.4
1 0 obj: Catalog → /Pages 2 0 R
2 0 obj: Pages → /Kids [3 0 R], /Count 1
3 0 obj: Page → /Parent 2 0 R, /MediaBox [0 0 612 792], /Resources << /Font << /F1 5 0 R >> >>, /Contents 4 0 R
4 0 obj: Content stream → BT /F1 12 Tf 50 700 Td <000102> Tj ET (byte codes for glyphs /g001, /g002, /g003)
5 0 obj: Font → /Type /Font /Subtype /Type1 /BaseFont /CustomNoMap /Encoding << /Type /Encoding /Differences [0 /g001 /g002 /g003] >>

Conclusion

All acceptance criteria are fully met by the existing no-mapping.pdf fixture. No additional work required.

Bead bf-512z1: Unicode recovery Phase 2 exit gate (≥90% recovery rate)
Bead bf-f0xqd: Corrected no-mapping.pdf ground truth from "ABC" to U+FFFD
Bead bf-1m30m: Regenerated no-mapping.pdf via generate_unicode_recovery_fixtures.rs
Plan Section TH-03: Test harness for unmapped glyph diagnostics

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