fix: increase sleep duration in dynamic channel test to allow processing

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

tests/integration.c

@@ -387,7 +387,9 @@ static int test_multiple_channels(void) {
         fprintf(stderr, "  FAIL: send note 60 failed\n");
         return 1;
     }
-    usleep(500000);
+    /* wait long enough for the looper's main loop to process the add command
+       (it sleeps for 1 second between checks, so 1.5 s is safe) */
+    usleep(1500000);
 
     int found = 0;
     const char **ports = jack_get_ports(client, NULL, JACK_DEFAULT_AUDIO_TYPE, 0);