Pre-scan lines to identify "isolated" ones — short lines (1-6 words)
with paragraph breaks both before AND after. These are heading
candidates even at body font size, common in academic papers
("Acknowledgements", "Limitations", "B.3 Prompt Engineering").
Inspired by opendataloader's HeadingProcessor which passes prevNode
and nextNode context to the heading probability scorer.
The isolated signal (+0.3) combines with rarity/bold/standalone
signals. A per-page density guard prevents false positives on
multi-column pages where many lines appear isolated. Continuation
word detection (ending in "the", "and", etc.) filters wrapped
paragraph lines.
MHS=0 docs: 18→13. MHS-S +0.004. No regressions.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
