dbus: fix streaming performance

- sendNotification now async (fire-and-forget goroutine)
- ChatUpdated coalescing interval 50ms -> 150ms to reduce signal flood

main.go

@@ -73,7 +73,7 @@ func (e *chatEmitter) append(text string) {
 	e.buf += text
 	if !e.running {
 		e.running = true
-		e.timer = time.AfterFunc(50*time.Millisecond, e.flush)
+		e.timer = time.AfterFunc(150*time.Millisecond, e.flush)
 	}
 	e.mu.Unlock()
 }
@@ -707,6 +707,7 @@ func (m *SessionManager) DismissDetached(sessionID string, pid int32) (bool, *db
 // --- Notifications ---
 
 func (m *SessionManager) sendNotification(title, body string) {
+	go func() {
 		obj := m.conn.Object("org.freedesktop.Notifications", "/org/freedesktop/Notifications")
 		obj.Call("org.freedesktop.Notifications.Notify", 0,
 			"ollie-dbus",      // app_name
@@ -718,6 +719,7 @@ func (m *SessionManager) sendNotification(title, body string) {
 			map[string]dbus.Variant{}, // hints
 			int32(5000),       // timeout ms
 		)
+	}()
 }
 
 // --- Session Persistence ---