GitHub Action publishes changelogs; stalled polling self-heals

Added

• GitHub Action for publishing changelogs — a new publish-changelog Action diffs a changelog file on each push, maps changed sections onto upserted releases, and posts them to your Releases Index source; re-running the same commit is a no-op, and URL templates support heading permalink, date, version, and key formats.

Fixed

• Release cards no longer show pixelated avatar crops as inline media — the media filter now rejects CDN transform thumbnails where both resolved dimensions are ≤128 px (Cloudinary path transforms and imgix/Vercel query params), so only full-resolution editorial images appear.
• Sources that silently stopped polling now self-heal — a successful manual fetch or re-enable re-arms the actor, and the hourly heartbeat folds unmanaged active sources into its pass so dead alarms recover within one tick rather than waiting out a full polling window.