feat(surface): switch app shells when the viewport crosses the phone threshold

The mobile-vs-desktop surface is stamped once at boot, so a browser
window narrowed past the phone threshold kept the desktop shell (and
its legacy squeezed layout) until a manual reload. A viewport watcher
now reloads into the other shell once the resize settles — the same
mechanism the old Settings toggle used. Fixed shells (Capacitor,
desktop, VS Code) and ?surface= overrides never switch.

With the new mobile app reachable this way, the old/new mobile layout
preference is gone: phones always get the mobile app.

packages/ui/src/lib/i18n/messages/es.settings.ts

@@ -1890,9 +1890,6 @@ export const settingsDict = {
   "settings.voice.page.field.ttsInputModeSummarized": "resumido",
   "settings.openchamber.visual.section.colorMode": "Modo de color",
   "settings.openchamber.visual.section.colorModeAndTheme": "Modo de color y tema",
-  "settings.openchamber.visual.section.mobileLayout": "Diseño móvil",
-  "settings.openchamber.visual.option.mobileLayout.default": "Anterior",
-  "settings.openchamber.visual.option.mobileLayout.new": "Nuevo",
   "settings.openchamber.visual.section.localization": "Localización",
   "settings.openchamber.visual.section.spacingAndLayout": "Espaciado y diseño",
   "settings.openchamber.visual.section.densityAndType": "Densidad y tipografía",