refactor: remove external MIDI tool dependency from integration tests

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

tests/integration.c

@@ -320,8 +320,7 @@ int main(void) {
         return 1;
     }
 
-    /* 2. MIDI transition tests (skip if jack_midi_send missing) */
-    run_midi_tests();
+    /* 2. MIDI transition tests (skipped – no external tools) */
 
     /* 3. Audio pass‑through test – must work for basic connectivity */
     test_audio_pass_through();