Address round-4 review on PR #914:
- glyph_corruption_ratio <= 0 now disables the signal (previously `control_ratio
> 0` fired on any single C0 control byte), matching the "0 disables" convention
used elsewhere (document_max_pdf_size_mb) and the config comment. Add a
zero-disables test.
- Correct the document_escalation_suppressed_total comment: corrupt_glyphs CAN
appear there in the narrow case where structured is unregistered and OCR is
registered-but-disabled (evaluate_escalation follows minimum="structured" past
the missing rung to a gated-off OCR). Add a test for that suppressed decision.
- Add a test for the double-corruption edge: a structured re-extract that is also
glyph-corrupt escalates structured->ocr with reason corrupt_glyphs.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
