fix: resolve cppcheck warnings for const pointer and static functions

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

src/looper.c

@@ -135,7 +135,7 @@ int process_callback(jack_nframes_t nframes, void *arg) {
                                                  memory_order_acquire);
     if (r != NULL) {
       if (state == STATE_LOOPING && atomic_load(&channels[c].loop_count) > 0) {
-        float *outf = (float *)out;
+        const float *outf = (const float *)out;
         ring_write(r, outf, nframes);
       }
     }