fix: mobile entry click and add fullscreen button

- Delay virtual controls creation until after game starts (ctrl overlay
  was intercepting title screen touches)
- Add touchstart handler on game container for mobile entry
- Add fullscreen button overlay in top-right corner
- Hide title text after game starts

source/input.js

@@ -83,7 +83,8 @@ c.onmouseup = (ev) => {
 
 // ─── Mobile virtual controls ───
 
-if (is_touch) {
+// Called from main.js after game start
+create_touch_controls = () => {
 	let ctrl = document.createElement('div');
 	ctrl.id = 'ctrl';
 	ctrl.innerHTML =
@@ -148,5 +149,5 @@ if (is_touch) {
 			if (t.identifier === touch_id) touch_id = null;
 		}
 	});
-}
+};