feat: add ncurses-based TUI frontend with 8x8 clip grid and keyboard controls

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

main.c

@@ -3,6 +3,7 @@
 #include <signal.h>
 #include <unistd.h>
 #include "engine.h"
+#include "tui.h"
 
 static Engine engine;
 static volatile int keep_running = 1;
@@ -71,13 +72,13 @@ int main(int argc, char *argv[]) {
     printf("Sample rate: %u Hz\n", engine.sample_rate);
     printf("Press Ctrl+C to stop\n\n");
     
-    // Main loop
-    while (keep_running) {
-        sleep(1);
-    }
+    // Initialize and run TUI
+    tui_init(&engine);
+    tui_run(&engine);
+    tui_cleanup();
     
     // Cleanup
-    printf("\nShutting down...\n");
+    printf("\nShutting down...\n");  // This line may not be reached if tui_run returns
     engine_stop(&engine);
     engine_cleanup(&engine);