fix: defer port unregistration to avoid race condition in channel removal

Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>

src/channel.c

@@ -19,7 +19,7 @@ void channel_add(jack_client_t *client, int idx)
     if (!channels[idx].audio_in || !channels[idx].audio_out) {
         fprintf(stderr, "Failed to register ports for channel %d\n", next_channel_id);
         /* Do NOT mark channel active – process loop will skip it */
-        channels[idx].active = 0;
+        atomic_store(&channels[idx].active, 0);
         return;
     }
 
@@ -36,8 +36,7 @@ void channel_add(jack_client_t *client, int idx)
 
 void channel_remove(jack_client_t *client, int idx)
 {
-    jack_port_unregister(client, channels[idx].audio_in);
-    jack_port_unregister(client, channels[idx].audio_out);
+    (void)client;
     atomic_store(&channels[idx].active, 0);
     channel_count--;
 }