chore: update featherChat submodule to v0.0.38 (feature/wzp-call-infrastructure)
featherChat now implements:
- FC-2: Call state management (calls.rs, CallState, sled persistence)
- FC-3: WS call signal routing (Offer→Ringing, Answer→Active, Hangup→Ended)
- FC-5: Group-to-room mapping (hash_room_name — same convention as WZP)
- FC-6: Presence API (online/devices per fingerprint, batch query)
- FC-7: Missed call notifications (sled storage, retrieval endpoint)
Only FC-10 (web bridge shared auth) remains on FC side.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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