* fix(headings): digit-only lines do not define heading tiers
A large bold page number (14pt folio over 11pt body) claimed tier 0:
every real heading demoted one level document-wide, and the bold-size
fallback (which requires an empty tier list) was blocked for documents
whose headings match body size.
Bench-neutral (MHS scores relative hierarchy); pdf-evals: 18 docs get
their heading levels back (#### -> ###), semantic composite +0.0006,
no percentile down.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
* fix(headings): exclude digit-only lines from the bold fallback tier pass too
The exclusion in the main pass wasn't enough: with the page-number
tier gone, the bold fallback re-collected the same bold folio. Also
regenerates the thermo-freon12 snapshot (cosmetic churn on the
scrambled legend fixture).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
