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>

crates/wzp-client/tests/dual_path.rs

@@ -118,6 +118,7 @@ async fn dual_path_direct_wins_on_loopback() {
         "test-room".into(),
         "call-test".into(),
         None, // Phase 5: tests use fresh endpoints (no shared signal)
+        None, // Phase 7: no IPv6 endpoint in tests
     )
     .await
     .expect("race must succeed");
@@ -160,6 +161,7 @@ async fn dual_path_relay_wins_when_direct_is_dead() {
         "test-room".into(),
         "call-test".into(),
         None, // Phase 5: tests use fresh endpoints (no shared signal)
+        None, // Phase 7: no IPv6 endpoint in tests
     )
     .await
     .expect("race must succeed via relay fallback");
@@ -198,6 +200,7 @@ async fn dual_path_errors_cleanly_when_both_paths_dead() {
         "test-room".into(),
         "call-test".into(),
         None, // Phase 5: tests use fresh endpoints (no shared signal)
+        None, // Phase 7: no IPv6 endpoint in tests
     )
     .await;
     let elapsed = start.elapsed();