* Expose workspace webhooks through the API and MCP.
The same create/update/test/rotate/replay/delete flow now lives in Actions so the web UI, REST API, and MCP tools stay in lockstep.
* Keep webhook validation local to each web, API, and MCP entry point.
* Extract MCP webhook rules into request classes and close remaining API/MCP review gaps.
* Tighten webhook updates to a field whitelist and reset failures only on re-enable.
* Treat a mismatched webhook replay as not found and mark secret rotation destructive.
