test(ui): cover rail exclusion and add the panel-resize QA harness

The right-rail test now proves a .panel-floating panel is neither
measured, allocated nor auto-collapsed while its docked sibling still is.
scripts/qa-panel-resize.mjs drives the CCTV panel in a real browser:
lift-out by header drag, all eight handles with the opposite edge pinned,
minimum size, reload restore and double-click snap-back. Its pure helpers
sit behind a main guard so src/tooling/panelResizeQa.test.mjs can check
them without a browser. Run it with `npm run qa:panel-resize`.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/ui/panelRails.test.mjs

@@ -243,6 +243,28 @@ test('right layout retains Display allocation during measurement and caps restor
   );
 });
 
+test('right rail neither measures nor allocates a panel floating out of it', () => {
+  const f = fixture('right');
+  f.expand(f.first, 900);
+  f.expand(f.second, 300);
+  f.first.classList.add('panel-floating');
+  f.first.style.setProperty('--right-panel-allocated-height', '500px');
+  f.first.writes.length = 0;
+  f.run();
+  assert.equal(f.stack.dataset.expandedCount, '1');
+  assert.deepEqual(
+    f.first.writes,
+    [],
+    'a floating panel keeps whatever inline style it left the rail with',
+  );
+  assert.equal(f.first.getAttribute('aria-hidden'), undefined);
+  assert.equal(f.first.classList.contains('layout-auto-collapsed'), false);
+  assert.ok(
+    f.second.style.getPropertyValue('--right-panel-allocated-height'),
+    'the docked panel still receives its allocation',
+  );
+});
+
 test('right rail aligns to the current left rail and excludes hidden obstacles', () => {
   const f = fixture('right');
   f.options.leftStack.rect.top = 200;