Allow trusted local plugins to register complete coding-agent providers through the existing agent lifecycle. Includes direct and ACP implementations, SVG provider icons, custom timeline items, runnable examples, and public authoring documentation.
Closes#3547Closes#3556
Make provider catalogs compact and content-addressed so repeat launches can reuse the persisted snapshot instead of transferring it again. Remove eager global catalog loading and the stopped-agent defensive tail fetch, while keeping sequence-gap and reconnect recovery as the correctness paths. Add an opt-in production-ID Android profiling build for local startup traces.