fix(parse-pdf): F4 mojibake.pdf via pikepdf surgery; preserve 1-page invariant (Bug #4)
v0.20.0 sub-item 1 dogfood report 의 Bug #4 — F4 mojibake.pdf 의 lopdf
`get_pages()` count = 0 (Pages tree broken). root cause = 기존 byte-
level `re.sub` + manual startxref edit 가 lopdf strict load 통과시키지만
Pages dict 의 `/Kids` reference 깨짐.
- `tests/fixtures/_synth/mojibake.py`: full rewrite — replace byte-level
`re.sub` + manual startxref with pikepdf open+inject-dummy-ToUnicode+
del+save (auto xref regen). HYSMyeongJo-Medium CID font: CID font 이
ToUnicode 를 자체 생성하지 않아 dummy stream 을 inject 후 strip
(removed=1 invariant). Exit codes 2/3/4 for invariant fail.
- `crates/kebab-parse-pdf/tests/fixtures/mojibake.pdf`: regenerate via
pikepdf — 1 valid page, no /ToUnicode marker, byte-identical 후 reproducible.
- `crates/kebab-parse-pdf/tests/snapshots/vector_pdf_canonical.json`:
regen via 2-run cargo test pattern (hand-rolled unwrap_or_else baseline
bootstrap, no insta crate).
- `crates/kebab-parse-pdf/tests/text_extractor_regression.rs`: append 3
invariant test — (1) lopdf 1-page, (2) /ToUnicode marker absent,
(3) PdfTextExtractor 1-block invariant.
- `crates/kebab-parse-pdf/src/text_quality.rs`: f4_fixture_ratio_under_threshold
threshold 0.3 → 0.5 (production valid_ratio_threshold 기본값). 구 broken
fixture (pages=0) 는 extract_text="" → ratio=0.0; 신 fixed fixture 는
CID 2-byte fallback decode → ratio≈0.375 — 여전히 OCR trigger 조건 충족.
spec: docs/superpowers/specs/2026-05-27-v0.20-sub1-bugfix-spec.md (§5)
plan: docs/superpowers/plans/2026-05-27-v0.20-sub1-bugfix-plan.md (Step 4)
prior: 241ded5 (Step 3 integration test)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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