Play through the first camera that is switched on

The game view took whatever camera came first in the scene, ignoring the
switch, so `enabled = false` on a camera did nothing and a second camera
never got its turn. `World.activeCamera()` now decides: of the cameras
switched on – the whole parent chain counted, as for any object – the
first in hierarchy order, and none on renders nothing at all. It is asked
per frame, so a graph switching cameras hands the view over immediately.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/e2e/03-play.mjs

@@ -13,7 +13,10 @@ export async function play(t) {
     evaluate,
     json,
     shot,
+    click,
     clickText,
+    dragAsset,
+    locate,
     press,
     holdKey,
     undo,
@@ -170,9 +173,73 @@ export async function play(t) {
     s.mode === 'play' && !info.rendering && info.visibleItems === 0,
     JSON.stringify(info),
   );
-  check('play without camera shows a notice', s.notice.includes('no camera'), s.notice);
+  check('play without camera shows a notice', s.notice.includes('No camera is switched on'), s.notice);
   await shot('10-play-no-camera');
   await stop();
   await undo();
   check('undo restored the camera object', (await objects()).length === 7);
+
+  // 7d. Which camera renders: a camera that is switched off is skipped like any other object, and
+  //     of those left the first in hierarchy order takes the view. The second camera is parked far
+  //     from the origin, so "seen through it" is provable – both crates fall outside its frame.
+  await select({ kind: 'object', holderId: 'scene1', objectId: 'o3' });
+  const enabledRow = await locate('Enabled');
+  // The checkbox sits right of the 64 px label column; locate() gives the label's text centre.
+  await click(enabledRow.x + 55, enabledRow.y);
+  await sleep(150);
+  check(
+    'the camera has the enabled switch like any other object',
+    (await object('o3')).overrides.enabled === false,
+    JSON.stringify((await object('o3')).overrides),
+  );
+  await play();
+  info = await gameInfo();
+  s = await state();
+  check(
+    'a switched-off camera renders nothing although it is still in the scene',
+    !info.rendering && info.camera === '' && info.visibleItems === 0,
+    JSON.stringify(info),
+  );
+  check('and the notice names the switch, not a missing camera', s.notice.includes('switched on'), s.notice);
+  await stop();
+
+  const centre = await json('__gm.viewportCenter()');
+  await dragAsset('cam', centre.x + 250, centre.y + 150);
+  const second = (await objects()).find((o) => !FIXTURE_IDS.includes(o.id));
+  check('a second camera is placed in the scene', Boolean(second), JSON.stringify(second));
+  await mutate(
+    `__gm.state.activeScene.objects.find(o => o.id === ${JSON.stringify(second.id)}).position.x = 5000`,
+  );
+  await play();
+  info = await gameInfo();
+  check(
+    'the switched-on camera takes over, and the game is seen through it: the crates at the origin are outside its frame',
+    info.camera === second.id && info.rendering && info.visibleItems === 0,
+    JSON.stringify(info),
+  );
+  await shot('10b-second-camera');
+  await stop();
+
+  await select({ kind: 'object', holderId: 'scene1', objectId: 'o3' });
+  const switchBackOn = await locate('Enabled');
+  await click(switchBackOn.x + 55, switchBackOn.y);
+  await sleep(150);
+  await play();
+  info = await gameInfo();
+  check(
+    'with both switched on the first camera in hierarchy order is the active one again',
+    info.camera === 'o3' && info.visibleItems === 2,
+    JSON.stringify(info),
+  );
+  await stop();
+
+  // Back to the fixture: the switch-on, the placement and the switch-off, newest first.
+  await undo();
+  await undo();
+  await undo();
+  check(
+    'undo leaves the fixture as it was, camera on and without an override',
+    (await objects()).length === 7 && Object.keys((await object('o3')).overrides).length === 0,
+    JSON.stringify((await object('o3')).overrides),
+  );
 }