docs: mark WZP-FC-1 and WZP-FC-4 as DONE (featherChat v0.0.21)

featherChat commit 064a730 implements:
- CallSignal WireMessage variant with Offer/Answer/ICE/Hangup/Reject/Ringing/Busy
- POST /v1/auth/validate endpoint returning fingerprint + alias

WZP can now:
- Send SignalMessage as JSON in CallSignal.payload through FC's E2E channel
- Verify FC bearer tokens on the relay via the validate endpoint

Next: WZP-S-2 (relay auth) and WZP-S-3 (signaling bridge in client)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/INTEGRATION_TASKS.md

@@ -71,10 +71,16 @@ Based on featherChat commit 65f6390 — FUTURE_TASKS.md with WZP integration ite
 
 ## featherChat-Side Tasks (their responsibility, we support)
 
-### WZP-FC-1. Add CallSignal WireMessage variant — 2-4h
+### WZP-FC-1. Add CallSignal WireMessage variant — DONE (v0.0.21, 064a730)
+- `CallSignal { id, sender_fingerprint, signal_type, payload, target }`
+- `CallSignalType`: Offer, Answer, IceCandidate, Hangup, Reject, Ringing, Busy
+- payload field is String — WZP puts JSON-serialized SignalMessage here
+- target field: peer fingerprint (1:1) or room name (group)
 ### WZP-FC-2. Call state management + sled tree — 1-2d
 ### WZP-FC-3. WS handler for call signaling — 0.5d
-### WZP-FC-4. Auth token validation endpoint — 2-4h
+### WZP-FC-4. Auth token validation endpoint — DONE (v0.0.21, 064a730)
+- `POST /v1/auth/validate { "token": "..." }`
+- Returns: `{ "valid": true, "fingerprint": "...", "alias": "..." }`
 ### WZP-FC-5. Group-to-room mapping — 1d
 ### WZP-FC-6. Presence/online status API — 0.5-2d
 ### WZP-FC-7. Missed call notifications — 0.5d