Single docs articles now show a breadcrumb trail above the title, e.g.
Home › Documentation › Developer Guide › Installing Soames. Ancestors link
to their pages; the current article is the final, non-linked crumb.

- wp.ts: docAncestors() walks the parentDatabaseId chain (data, not the URI,
  since slugs don't always match titles) and returns ancestors root→parent.
- Breadcrumbs.tsx: static presentational component; CSS-drawn separators,
  aria-label="Breadcrumb" + aria-current on the current page.
- docs/[...slug].astro: assembles the crumb list and renders it in the header.
- overrides.css: .soames-breadcrumbs styling to match the docs nav.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>