fix: remove misplaced signal call and use _Exit in signal handler

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

tui.c

@@ -33,9 +33,6 @@ static int state_to_color(ClipState state) {
         case CLIP_STOPPED: return COLOR_STOPPED;
         default: return COLOR_EMPTY;
     }
-    
-    // Install signal handler for Ctrl+C
-    signal(SIGINT, handle_sigint);
 }
 
 // Get clip index from grid position
@@ -145,7 +142,7 @@ static void draw_grid(void) {
 static void handle_sigint(int sig) {
     (void)sig;
     tui_cleanup();
-    _exit(1);
+    _Exit(1);
 }
 
 void tui_init(Engine *engine) {