v0.7.1 — accurate doc references (HTML attrs + directory links)

Veridge 0.7.1

Two fixes to documentation-reference accuracy, so gate / health report real drift
instead of false positives. Deterministic, no behaviour change for code/import edges.

Fixed

• HTML references come from href/src attributes, not the markdown/prose heuristics.
  A bundled doc page with inlined minified JS (e.g. t[s](i+1)) used to make the markdown
  link regex ](…) fire and record garbage like i+1 / "z","!!!!!" as broken references.
  HTML now uses a dedicated, extension-filtered attribute extractor (URLs dropped) — the noise
  is gone and genuine HTML links are resolved.
• A link to a real project directory is no longer "broken." A markdown link whose target
  is an existing directory (e.g. [the web app](apps/web)) resolved to no file node and was
  reported broken; it is now treated as valid. Genuinely missing targets are still flagged.

No changes to the symbol / import / call graph; same zero-dependency core.