ci: remove dead registry-api notification workflow - #334

Deletes the inert .github/workflows/notify.yml; the PR's rationale checks out — the dispatch defaulted to this repo, GITHUB_TOKEN cannot dispatch cross-repo, and no repository_dispatch listener exists, so the job only ever burned a runner and a 90s sleep. CI-only with no dangling references, correctly needs no changeset; the sole note is that the Cursor pass produced no output.