fix: replace usleep with nanosleep and fix const correctness

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

src/looper.c

@@ -47,8 +47,8 @@ int process_callback(jack_nframes_t nframes, void *arg) {
       continue;
     }
 
-    jack_default_audio_sample_t *in =
-        (jack_default_audio_sample_t *)jack_port_get_buffer(
+    const jack_default_audio_sample_t *in =
+        (const jack_default_audio_sample_t *)jack_port_get_buffer(
             channels[c].audio_in, nframes);
     jack_default_audio_sample_t *out =
         (jack_default_audio_sample_t *)jack_port_get_buffer(
@@ -82,6 +82,7 @@ int process_callback(jack_nframes_t nframes, void *arg) {
           if (channels[c].record_pos < LOOP_BUF_SIZE)
             channels[c].loop_buffer[channels[c].record_pos++] =
                 ((const float *)in)[i];
+          // cppcheck-suppress unreadVariable
           ((float *)out)[i] = ((const float *)in)[i];
         }
       } else {

src/main.c

@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <time.h>
 
 int main(int argc, char *argv[]) {
   (void)argc;
@@ -41,7 +42,7 @@ int main(int argc, char *argv[]) {
 
   while (1) {
     looper_process_commands(client);
-    usleep(50000); /* check commands every 50 ms */
+    { struct timespec ts = { .tv_sec = 0, .tv_nsec = 50000000 }; nanosleep(&ts, NULL); } /* check commands every 50 ms */
   }
 
   jack_client_close(client);