The pkg/urlmentions package consumes version 1.0 of the public URL mentions protocol.
Provider indexes:
- https://listen.waylonwalker.com/.well-known/url-mentions.json
- https://brainrot.waylonwalker.com/.well-known/url-mentions.json
urlmentions.Client.Fetch(ctx, endpoint) retrieves all pages and returns a map
from provider-supplied references[].normalized_url to source entries.
It bounds response sizes and page counts, rejects non-HTTPS starting URLs,
and disallows cross-origin pagination. The caller should use an HTTP client
with redirects restricted to the same origin and enforce a build-time budget.
This is phase one only. The package is not registered as a build plugin, does not fetch either provider automatically, and does not render UI yet. Follow-up work: align canonical URL normalization with the provider protocol; cache provider pages/ETags; configure providers; map post canonical, external target, and reader URLs; SSR accessible favicon badges with no-JS fallbacks; graceful offline builds and snapshot tests.
Do not treat this PR as production feature-complete.