fix: make loop_count atomic and increase remove channel delay

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

tests/integration.c

@@ -819,7 +819,7 @@ static int test_remove_channel(void) {
         fprintf(stderr, "  FAIL: send note 61 failed\n");
         return 1;
     }
-    safe_usleep(1500000);
+    safe_usleep(3000000);
     /* verify channel1_input has disappeared */
     ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);
     int still_found = 0;