feat(ux): SSE disconnect/reconnect banner in session view (#42)

Shows amber 'Reconnecting… (attempt N)' banner when SSE is down.
Shows brief green 'Connected ✓' flash on reconnect (useRef transition
to avoid atomic state reset bug where lastDisconnectAt resets with
reconnectAttempts in the same set() call).

Banner disappears automatically when SSE is stable.

Updates CUA scenario to check for both ASCII and Unicode ellipsis.

Closes #42

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

app/session/[id].tsx

@@ -125,6 +125,11 @@ export default function SessionScreen() {
   const shortDir = getShortDir(currentSession?.directory)
   const [showScrollButton, setShowScrollButton] = useState(false)
 
+  // SSE reconnect banner
+  const reconnectAttempts = useEvents((s) => s.reconnectAttempts)
+  const [showConnectedFlash, setShowConnectedFlash] = useState(false)
+  const prevReconnecting = useRef(false)
+
   // Voice input — transcript appends to the text input on completion
   const speech = useSpeech(
     useCallback((text: string) => {
@@ -363,6 +368,19 @@ export default function SessionScreen() {
     if (!loadingMore) loadingTriggered.current = false
   }, [loadingMore])
 
+  // Detect reconnecting → stable transition for the "Connected ✓" flash.
+  // reconnectAttempts and lastDisconnectAt reset in the same set() call, so we
+  // can't use lastDisconnectAt alone; a useRef tracks the prior reconnecting state.
+  useEffect(() => {
+    const isReconnecting = reconnectAttempts > 0
+    if (prevReconnecting.current && !isReconnecting) {
+      setShowConnectedFlash(true)
+      const t = setTimeout(() => setShowConnectedFlash(false), 2000)
+      return () => clearTimeout(t)
+    }
+    prevReconnecting.current = isReconnecting
+  }, [reconnectAttempts])
+
   const handlePermissionReply = async (requestID: string, reply: "once" | "always" | "reject") => {
     if (!sessionClient || !sessionID) return
     // Snapshot for rollback
@@ -486,6 +504,18 @@ export default function SessionScreen() {
           onClose={() => setShowInfo(false)}
         />
 
+        {/* SSE reconnect/connected banner */}
+        {reconnectAttempts > 0 && (
+          <View style={[s.banner, s.bannerReconnecting]}>
+            <Text style={s.bannerText}>Reconnecting\u2026 (attempt {reconnectAttempts})</Text>
+          </View>
+        )}
+        {showConnectedFlash && reconnectAttempts === 0 && (
+          <View style={[s.banner, s.bannerConnected]}>
+            <Text style={s.bannerText}>Connected ✓</Text>
+          </View>
+        )}
+
         {isLoading ? (
           <View style={s.loading}>
             <ActivityIndicator size="large" color={isDark ? "#ffffff" : "#0a0a0a"} />
@@ -821,4 +851,14 @@ const s = StyleSheet.create({
   dirBadgeDark: { backgroundColor: "#1a1a1a" },
   dirText: { fontSize: 12, color: "#666666", fontWeight: "500" },
   dirTextDark: { color: "#888888" },
+
+  // SSE reconnect/connected banner
+  banner: {
+    paddingHorizontal: 16,
+    paddingVertical: 6,
+    alignItems: "center",
+  },
+  bannerReconnecting: { backgroundColor: "#92400e" },
+  bannerConnected: { backgroundColor: "#065f46" },
+  bannerText: { color: "#ffffff", fontSize: 13, fontWeight: "500" },
 })