feat: add JACK audio looper with clip state machine and tests

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

main.c

@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include "engine.h"
+
+static Engine engine;
+static volatile int keep_running = 1;
+
+void signal_handler(int sig) {
+    keep_running = 0;
+}
+
+void print_usage(const char *program) {
+    printf("Usage: %s [options]\n", program);
+    printf("Options:\n");
+    printf("  -n <name>    JACK client name (default: jack-looper)\n");
+    printf("  -c <channel> MIDI control channel (default: 0)\n");
+    printf("  -h           Show this help\n");
+}
+
+int main(int argc, char *argv[]) {
+    const char *client_name = "jack-looper";
+    int control_channel = 0;
+    int opt;
+    
+    while ((opt = getopt(argc, argv, "n:c:h")) != -1) {
+        switch (opt) {
+            case 'n':
+                client_name = optarg;
+                break;
+            case 'c':
+                control_channel = atoi(optarg);
+                if (control_channel < 0 || control_channel > 15) {
+                    fprintf(stderr, "Control channel must be 0-15\n");
+                    return 1;
+                }
+                break;
+            case 'h':
+                print_usage(argv[0]);
+                return 0;
+            default:
+                print_usage(argv[0]);
+                return 1;
+        }
+    }
+    
+    // Initialize engine
+    if (engine_init(&engine, client_name) != 0) {
+        fprintf(stderr, "Failed to initialize engine\n");
+        return 1;
+    }
+    
+    engine.control_channel = control_channel;
+    
+    // Set up signal handler
+    signal(SIGINT, signal_handler);
+    signal(SIGTERM, signal_handler);
+    
+    // Start engine
+    if (engine_start(&engine) != 0) {
+        fprintf(stderr, "Failed to start engine\n");
+        engine_cleanup(&engine);
+        return 1;
+    }
+    
+    printf("JACK Looper started\n");
+    printf("Client name: %s\n", client_name);
+    printf("Control channel: %d\n", control_channel);
+    printf("Sample rate: %u Hz\n", engine.sample_rate);
+    printf("Press Ctrl+C to stop\n\n");
+    
+    // Main loop
+    while (keep_running) {
+        sleep(1);
+    }
+    
+    // Cleanup
+    printf("\nShutting down...\n");
+    engine_stop(&engine);
+    engine_cleanup(&engine);
+    
+    return 0;
+}