Two headings on the same page can generate the same anchor id, and every
link to it then resolves to whichever comes first. Nothing caught this
because the route manifest keeps anchors in a `Set`, so a repeat collapses
into one entry before any check runs, and the existing link validation only
asks whether an anchor exists, which a duplicate satisfies.
The generator now inspects each page's headings while they are still an
ordered list and fails with the offending pages and anchors. The scanning
and the duplicate check move to `heading.mts` so they are covered by tests
next to `getIdFromHeading`, which should keep this from coming back.
(cherry picked from commit 5e8a70a010)
This commit extracts the heading ID generation logic into a shared utility
and updates both the route generation script and the markdown pipeline to use it.
This ensures consistency between the generated routes and the rendered
documentation, and fixes an issue where custom heading IDs (`{#id}`)
were ignored during route generation.
Fixes#67200
Improves the symbol linking logic to handle Angular component selectors (e.g., ngCombobox). It attempts to convert Angular selector patterns to their corresponding class names, improving navigation to Angular API documentation.
Kam