Fix MIST gallery scene controls, video positioning and audio overlap

frontend/tests/screens.test.mjs

@@ -332,3 +332,27 @@ test("a redraw queued before pointerdown preserves the Return button until click
     manager.destroy();
   }
 });
+
+test("hover keeps image-button geometry and does not redraw screens for absent hover actions", async () => {
+  const { manager, calls } = setup();
+  const c = v => ({ k: 'const', v });
+  manager.screens.hoverTest = { params: [], props: {}, defaults: [], body: [
+    { w: 'imagebutton', args: [], body: [], props: { idle: c('idle.png'), hover: c('hover.png'), hover_sound: c('hover.ogg') } },
+  ] };
+  try {
+    manager.show('hoverTest');
+    const button = manager.layer.querySelector('.pg-simgbtn');
+    const images = [...button.querySelectorAll('img')];
+    assert.equal(images.length, 2, 'both state images participate in layout before hovering');
+    button.onmouseenter();
+    await settle();
+    assert.equal(manager.layer.querySelector('.pg-simgbtn'), button, 'no hover rebuild under the pointer');
+    assert.deepEqual([...button.querySelectorAll('img')], images, 'images stay attached across state changes');
+    assert.deepEqual(images.map(el => el.style.opacity), ['0', '1']);
+    assert.deepEqual(calls.play, [['sound', 'hover.ogg', false]]);
+    button.onmouseleave();
+    await settle();
+    assert.equal(manager.layer.querySelector('.pg-simgbtn'), button);
+    assert.deepEqual(images.map(el => el.style.opacity), ['1', '0']);
+  } finally { manager.destroy(); }
+});