fix(connect): install MediaPathReport oneshot BEFORE race starts

The peer's MediaPathReport can arrive while our dual_path::race is
still running. Previously, the oneshot was created AFTER the race
completed, so the recv loop had nowhere to deliver the report —
it was silently dropped, causing a 3s timeout and false relay
fallback on ~50% of calls.

Fix: create the oneshot and install it in SignalState BEFORE
starting the race. The oneshot::Receiver buffers the value so the
connect command can read it immediately after the race finishes.

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

desktop/src-tauri/src/lib.rs

@@ -415,6 +415,18 @@ async fn connect(
                     "relay_addr": relay_sockaddr.to_string(),
                     "own_reflex_addr": own_reflex_addr,
                 }));
+                // Phase 6 fix: install the oneshot BEFORE the race
+                // starts. The peer's MediaPathReport can arrive
+                // while our race is still running — if we set up
+                // the oneshot after the race, the recv loop has
+                // nowhere to send the report and it gets dropped,
+                // causing a 3s timeout and false relay fallback.
+                let (path_report_tx, path_report_rx) = tokio::sync::oneshot::channel::<bool>();
+                {
+                    let mut sig = state.signal.lock().await;
+                    sig.pending_path_report = Some(path_report_tx);
+                }
+
                 let room_sni = room.clone();
                 let call_sni = format!("call-{room}");
                 match wzp_client::dual_path::race(
@@ -456,12 +468,14 @@ async fn connect(
                             .unwrap_or(&room)
                             .to_string();
 
-                        // Install the oneshot for receiving the peer's report
+                        // The oneshot was installed BEFORE the race
-                        let (tx, rx) = tokio::sync::oneshot::channel::<bool>();
+                        // (see path_report_tx above) so the peer's
+                        // report is already buffered in path_report_rx
+                        // if it arrived during the race.
+                        let rx = path_report_rx;
                         let peer_direct_ok = {
                             let transport_for_report = {
-                                let mut sig = state.signal.lock().await;
+                                let sig = state.signal.lock().await;
-                                sig.pending_path_report = Some(tx);
                                 sig.transport.as_ref().cloned()
                             };
                             // Send our report