feat(rag): docs ingestion + UI/bus enhancements (P3 continuation)

fix: Python 3.10 compatibility - replace UTC import with timezone.utc

feat: WebLLM browser agent with PeerJS mesh, HybridRAG, news signals, and easter-egg ticker

fix: asyncio.get_running_loop() across backends; expand mesh/capability/model UI docs

feat: mesh graph tab, routing trace, QR invite, remove all fakes, specialized-node tests

feat: impl_ref gaps closed — Nemotron/OpenBMB backends, spec refs, extended UI, HOWTO, multi-node E2E

feat: Phase 2 (M14-M25, X05-X07) + Phase 3 experimental (M26-M31) + E2E tests + docs