One MainActivity, ever: a stacked instance made hang-up a no-op

The default launch mode stacked a second MainActivity — with a second
ViewModel, session and CallManager — whenever the app was re-entered.
The visible screen's Hang up then commanded a manager with no call while
the real call rang on underneath, and the peer never got the END.
singleTask, plus a 30s connect guard so an answered call whose ICE never
finds a path gives up out loud on both screens instead of sitting in
Connecting forever.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/AndroidManifest.xml

@@ -55,9 +55,20 @@
           presents as a corrupt install rather than as a missing key.
         -->
 
+        <!--
+          🔴 singleTask is load-bearing, not cosmetic. The default launch mode
+          stacks a NEW MainActivity — with a NEW ViewModel, session, poll loop
+          and CallManager — every time the app is entered through a
+          notification or a fresh launcher intent. Two instances means the
+          visible screen's Hang up commands a CallManager that has no call,
+          while the real call keeps ringing in the instance underneath: the
+          peer never receives the END, and "I ended the call but their phone
+          kept going" is exactly how it presents.
+        -->
         <activity
             android:name=".app.MainActivity"
             android:exported="true"
+            android:launchMode="singleTask"
             android:windowSoftInputMode="adjustResize">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

app/src/main/kotlin/io/flamenet/messenger/app/CallManager.kt

@@ -113,6 +113,23 @@ class CallManager(
     /** Gives up an unanswered outgoing call, like iOS's 45 s dial timeout. */
     private var dialGuard: Runnable? = null
 
+    /**
+     * Gives up a call that was answered but whose media never connected.
+     * Without it, an answer whose ICE cannot find a path — no TURN, hostile
+     * NAT — left BOTH screens sitting in "Connecting…" until someone forced
+     * the app closed.
+     */
+    private var connectGuard: Runnable? = null
+
+    private fun armConnectGuard() {
+        connectGuard?.let { main.removeCallbacks(it) }
+        val guard = Runnable {
+            if (state == State.CONNECTING) hangUp(notifyPeer = true, reason = "timeout")
+        }
+        connectGuard = guard
+        main.postDelayed(guard, CONNECT_TIMEOUT_MS)
+    }
+
     /** Main thread only. */
     private fun sendWhenGathered(send: (String) -> Unit) {
         onGathered = send
@@ -372,6 +389,7 @@ class CallManager(
                 dialGuard?.let { main.removeCallbacks(it) }
                 dialGuard = null
                 state = State.CONNECTING
+                armConnectGuard()
                 connection?.setRemoteDescription(
                     SimpleSdpObserver(),
                     SessionDescription(SessionDescription.Type.ANSWER, sdp),
@@ -390,6 +408,7 @@ class CallManager(
         pendingOffer = null
         val sdp = offer.sdp ?: return
         state = State.CONNECTING
+        armConnectGuard()
         val pc = open(turn, fromUser, offer.callId, offer.video) ?: run {
             state = State.IDLE
             return
@@ -458,6 +477,8 @@ class CallManager(
         gatherGuard = null
         dialGuard?.let { main.removeCallbacks(it) }
         dialGuard = null
+        connectGuard?.let { main.removeCallbacks(it) }
+        connectGuard = null
         val active = current
         if (notifyPeer && active != null) {
             // Best effort. Telling the other end is worth doing and is not
@@ -511,6 +532,7 @@ class CallManager(
     companion object {
         /** How long an unanswered outgoing call rings before giving up. */
         const val DIAL_TIMEOUT_MS = 45_000L
+        const val CONNECT_TIMEOUT_MS = 30_000L
 
         /**
          * How long to wait for ICE gathering before sending what we have. An