App 2.27.0: full-width Overview, a button hides the navigation

A small button in the Overview's top-right corner hides the app's
sidebar (or bottom bar) and brings it back; only on the Overview,
remembered, swiping still works. Emulator only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhzAVaUyqcw5PkGjz4mWW6

SPECS.md

@@ -131,6 +131,16 @@ tyre pressures, GPS (lat, lon, elevation, heading) and the is_* flags. It does *
   confirmed car facts, app structure, UI conventions, build/test/ship, documents. It replaces
   upstream's EVABRPUploader text. The test emulator is now in the flake: `nix run .#car-emulator`
   (Android 9 AOSP at 1920×720, 160 dpi; the car build installs as the system user — checked).
+- 2026-10-24 — App 2.27.0 (branch `styles-retro-future`): the Overview can go full width. A
+  small round button in its top-right corner (40 dp disc in a 72 dp touch area, over the pages)
+  hides the app's navigation (sidebar, or the bottom bar on narrow screens); its icon turns to
+  "shrink" and a second tap brings the navigation back. Only on the Overview: other pages
+  always show the navigation and no button, swiping between pages still works, and coming back
+  to the Overview restores full width. Remembered (`overview_fullscreen`). The top-right corner
+  was chosen after looking at all fifteen styles (top left covered Tiles' "Battery"); Minimal's
+  clock moved left of it. Checked on the emulator: toggle, swipe away and back, restart, Tiles
+  and MG at full width (`screenshots/nilsmg4-2.27.0-overview-fullscreen.png`); no crash. Not
+  tried on the car.
 - 2026-10-24 — App 2.26.0 (branch `styles-retro-future`): five more Overview styles, chosen to
   differ in arrangement as much as in look, on a new base class `ClusterCanvasView` (values,
   easing, null-safe formatting, animating only while something moves and the view is shown).