fix(sky): restore the Milky Way on teardown, tidy the anime QA script

- VisualEffects.destroy() puts skyBox.milkyWayVisibility back to 1, as it
  already restores the borrowed bloom stage, so a surviving viewer does not
  keep a faded sky.
- Rename scripts/qa-anime-space-mask.mjs to qa-anime-sky.mjs: rewrite the
  header for the current approach, drop --space-expr and --repo, import
  puppeteer as a package, reject unknown cases and count the milkyway case
  as reached only while the anime stage is on.
- Put both sky QA scripts under format:check.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/ui/visualEffects.test.mjs

@@ -179,6 +179,24 @@ test('the anime stage fades the Milky Way out with its own intensity', () => {
   f.effects.destroy();
 });
 
+test('destroying the effects gives a surviving viewer its Milky Way back', () => {
+  const f = fixture();
+  const sky = { milkyWayVisibility: 1 };
+  f.effects.viewer.scene.skyBox = sky;
+  f.effects.initStyles();
+  f.effects.startTransition('anime', 0, 1);
+  f.tick(250);
+  f.effects.stop();
+  const frozen = sky.milkyWayVisibility;
+  assert.ok(
+    frozen > 0 && frozen < 1,
+    'stop keeps the stages, and the fade, as they are',
+  );
+  f.effects.destroy();
+  assert.equal(sky.milkyWayVisibility, 1);
+  assert.equal(f.requests.at(-1), 'style-stage');
+});
+
 test('bloom retains its dead zone, normalized intensity and independent toggle', () => {
   const f = fixture();
   f.effects.initPostProcess();