fix(ui): show peer identity on direct P2P calls instead of "Waiting for participants"

On relay-mediated calls, the relay broadcasts RoomUpdate with the
participant list and pollStatus renders it. On direct P2P calls
neither peer joins the relay's media room, so RoomUpdate never
fires and the UI showed "Waiting for participants..." even though
audio was flowing bidirectionally.

Fix: track the peer's identity (fingerprint + alias) from the
signal plane in a `directCallPeer` variable:

- Set on incoming call from the DirectCallOffer (caller_fp +
  caller_alias)
- Set on outgoing call from the Call button click (target_fp)
- Cleared on showConnectScreen (call ended)

pollStatus now checks: if the engine's participant list is empty
AND directCallPeer is set, inject a synthetic participant entry
with relay_label = "P2P Direct". The participant row renders with
identicon + fingerprint + alias as normal, but grouped under a
"P2P Direct" header instead of "This Relay".

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

desktop/src/main.ts

@@ -835,6 +835,14 @@ async function doConnect() {
   }
 }
 
+// Phase 5.6: when we're in a direct P2P call (not relay-
+// mediated), the relay's room infrastructure never sends a
+// RoomUpdate because neither peer actually joined the room.
+// pollStatus sees an empty participant list and shows "Waiting
+// for participants...". Track the peer's identity from the
+// signal plane and render a synthetic participant entry instead.
+let directCallPeer: { fingerprint: string; alias: string | null } | null = null;
+
 function showCallScreen() {
   connectScreen.classList.add("hidden");
   callScreen.classList.remove("hidden");
@@ -855,6 +863,7 @@ function showConnectScreen() {
   connectBtn.disabled = false;
   connectBtn.textContent = "Connect";
   levelBar.style.width = "0%";
+  directCallPeer = null;
   if (statusInterval) { clearInterval(statusInterval); statusInterval = null; }
 }
 
@@ -975,14 +984,23 @@ async function pollStatus() {
     const pct = rms > 0 ? Math.min(100, (Math.log(rms) / Math.log(32767)) * 100) : 0;
     levelBar.style.width = `${pct}%`;
 
-    // Participants grouped by relay
-    if (st.participants.length === 0) {
+    // Participants grouped by relay. For direct P2P calls the
+    // relay never sends a RoomUpdate (neither peer joins the
+    // relay's media room) so st.participants is empty. If we
+    // have a directCallPeer from the signal plane, inject a
+    // synthetic entry so the UI shows who we're talking to.
+    const displayParticipants =
+      st.participants.length === 0 && directCallPeer
+        ? [{ ...directCallPeer, relay_label: "P2P Direct" }]
+        : st.participants;
+
+    if (displayParticipants.length === 0) {
       participantsDiv.innerHTML = '<div class="participants-empty">Waiting for participants...</div>';
     } else {
       participantsDiv.innerHTML = "";
       // Group by relay_label (null = this relay)
       const groups: Record<string, typeof st.participants> = {};
-      st.participants.forEach((p: any) => {
+      displayParticipants.forEach((p: any) => {
         const relay = p.relay_label || "This Relay";
         if (!groups[relay]) groups[relay] = [];
         groups[relay].push(p);
@@ -1430,6 +1448,10 @@ callBtn.addEventListener("click", async () => {
   const target = targetFpInput.value.trim();
   if (!target) return;
   callStatusText.textContent = "Calling...";
+  // Remember the target for P2P participant display — on a
+  // direct call the relay never sends RoomUpdate so pollStatus
+  // would otherwise show "Waiting for participants...".
+  directCallPeer = { fingerprint: target, alias: null };
   try {
     await invoke("place_call", { targetFp: target });
   } catch (e: any) {
@@ -1473,6 +1495,11 @@ listen("signal-event", (event: any) => {
     case "incoming":
       incomingCallPanel.classList.remove("hidden");
       incomingCaller.textContent = `From: ${data.caller_alias || data.caller_fp?.substring(0, 16) || "unknown"}`;
+      // Remember the peer for the P2P participant display.
+      directCallPeer = {
+        fingerprint: data.caller_fp || "",
+        alias: data.caller_alias || null,
+      };
       // Start ringing + fire a system notification. Both stop in
       // the hangup/answered/accepted paths below (and via the
       // accept/reject button handlers).