feat(ui): phone layout with a bottom tab bar and one panel sheet at a time

At 720px and narrower the globe stays full screen and a bottom tab bar (Layers,
Cameras, Context, Search, More) opens one bottom sheet at a time, presenting the
existing rail and dock panels in place. Sheets borrow panels without persisting
or sharing them and put back what they changed. Cockpit, recording and clean
view close the sheet; scene playback keeps STOP reachable. Focus moves into the
sheet and back to its tab, the required attribution stays visible above the
voice control and any sheet, and the page uses safe-area insets. Wider
viewports are unchanged.

Adapted from the phone tab-shell proposed in #203 by @blearymoth.

src/ui/panelRails.test.mjs

@@ -21,7 +21,7 @@ test('Display uses an inner scroll body only in Cyber', () => {
 });
 
 test('Cyber restores one expanded owner, keeps launchers, and restores other theme preferences', () => {
-  for (const mobile of [false, true]) {
+  for (const mobile of [false]) {
     const f = fixture('right', {
       mobile,
       hud: { visible: true, variant: 'cyber' },
@@ -50,6 +50,22 @@ test('Cyber restores one expanded owner, keeps launchers, and restores other the
   }
 });
 
+test('Cyber keeps no accordion on phones, where the rail is presented as tab sheets', () => {
+  // A sheet (for example Cameras: CCTV with Street Level) shows several of the
+  // rail's panels at once; the accordion would collapse all but one.
+  const f = fixture('right', {
+    mobile: true,
+    hud: { visible: true, variant: 'cyber' },
+  });
+  f.expand(f.first, 250);
+  f.expand(f.second, 250);
+  f.options.preferredPanelId = f.second.id;
+  f.run();
+  assert.equal(f.first.classList.contains('collapsed'), false);
+  assert.equal(f.first.classList.contains('cyber-accordion-collapsed'), false);
+  assert.equal(f.second.classList.contains('collapsed'), false);
+});
+
 test('Cyber restored accordion prefers keyboard focus when no explicit owner exists', () => {
   const f = fixture('right', { hud: { visible: true, variant: 'cyber' } });
   f.expand(f.first, 250);