Plugin idea: WebSub/PubSubHubbub hub (blocked on api.events) #10

A WebSub hub: publishers ping the hub on change, the hub fans out to subscribers. Naturally wants api.events.onResourceChange (see REPORT.md) to notice pod changes without polling, and makes outbound POSTs to subscriber callback URLs (SSRF gate needed).

Good candidate after the events seam lands — until then it degrades to the same poll-based approach as the webhooks idea (#file-a-webhooks-issue). Documenting the wall is itself a useful finding.

Copy from: notifications/, corsproxy/ (gate), rss/ (walk). See AGENT.md / NOTES.md.