Fix: Propagate user exit signal to break animation loop

**CRITICAL BUG FIX**: When using -l (loop), the outer loop in main.rs
was restarting the animation even after user pressed exit keys.

Changes:
- render() now returns Result<bool> instead of Result<()>
- Returns true when user presses exit key (q/ESC/Ctrl+C)
- Returns false when animation completes naturally
- main.rs checks return value and breaks loop on user exit

This fixes the infinite loop issue where pressing q/ESC/Ctrl+C
had no effect when using the -l flag.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/main.rs

@@ -61,8 +61,14 @@ async fn run_piglet(args: PigletCli) -> Result<()> {
 
     // Run animation
     loop {
-        animation_engine.run(&mut terminal).await?;
+        let user_exited = animation_engine.run(&mut terminal).await?;
 
+        // If user pressed exit key, stop looping
+        if user_exited {
+            break;
+        }
+
+        // If not looping, stop after one animation
         if !args.loop_animation {
             break;
         }