fix: add missing jack midi header and suppress unused parameter warnings

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

src/main.c

@@ -3,6 +3,7 @@
 #include <unistd.h>
 #include <string.h>
 #include <jack/jack.h>
+#include <jack/midiport.h>
 
 typedef enum {
     STATE_IDLE,
@@ -22,6 +23,7 @@ static jack_client_t *client;
 
 static int process(jack_nframes_t nframes, void *arg)
 {
+    (void)arg;
     jack_default_audio_sample_t *in  = (jack_default_audio_sample_t *) jack_port_get_buffer(input_port, nframes);
     jack_default_audio_sample_t *out = (jack_default_audio_sample_t *) jack_port_get_buffer(output_port, nframes);
 
@@ -101,6 +103,8 @@ static void jack_shutdown(void *arg)
 
 int main(int argc, char *argv[])
 {
+    (void)argc;
+    (void)argv;
     const char *client_name = "looper";
     jack_options_t options = JackNullOption;
     jack_status_t status;