Sherlodoc Phase 2: per-heading entries for mld pages
Extend from_page in skeleton.ml to emit one child entry per heading
in addition to the whole-page entry. Each heading entry uses the
heading's Label.t identifier (which carries the fragment anchor) and
stores the heading text as its doc content for tokenisation.
Before: searching for a word returns only the page.
After: searching returns the page AND the specific heading, with a
qualified name that includes the anchor (e.g.
ht.heading-test.section-about-parseff).
Verified via sherlodoc index + search on a test fixture with two
headings: "section about parseff" and "section about tessera". Each
heading appears as a separate search result, and searching for
"section" returns both headings.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>