fix(relay): debug tap signal logging, dual_path test regression, PRD updates

- Add log_signal() and log_event() to DebugTap for RoomUpdate,
  QualityDirective, join/leave lifecycle events (task #11)
- Fix dual_path.rs Phase 7 regression: add missing ipv6_endpoint arg
  to 3 race() call sites
- Update PRDs to reflect actual implementation status: mark adaptive
  quality, coordinated codec, P2P, network awareness, protocol analyzer
- Update PROGRESS.md with QualityDirective gap and dual_path regression

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

docs/PRD-network-awareness.md

@@ -103,7 +103,7 @@ Sentinel value `0xFF` means "no change pending". The recv task polls on every re
 
 ### Tauri Desktop App (com.wzp.desktop)
 
-The Tauri engine doesn't use `AdaptiveQualityController` — quality is resolved once at call start. Adding network monitoring requires first adding adaptive quality to the Tauri call engine, which is a larger change.
+~~The Tauri engine doesn't use `AdaptiveQualityController` — quality is resolved once at call start.~~ **Update (2026-04-13):** Desktop now has `AdaptiveQualityController` wired into the recv task with `pending_profile` AtomicU8 bridge. Network monitoring on desktop is now feasible — the blocker was adaptive quality, which is done. Remaining work: platform-specific network change detection (macOS: `SCNetworkReachability` or `NWPathMonitor`; Linux: `netlink` socket).
 
 ### Mid-Call ICE Re-gathering