App 2.19.2: Full screen for CarPlay (experiment)

Adds com.allgo.carplay.service to immersive.full in Android 9's
policy_control setting when switched on, removes only that entry when
off. Car build (system user) only.

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

SPECS.md

@@ -118,6 +118,15 @@ 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).
+- 2026-10-23 — App 2.19.2: Settings → "Full screen for CarPlay (experiment)". The Logs tab showed
+  CarPlay on the car as `com.allgo.carplay.service/.CarPlayActivity`, an ordinary activity. The
+  switch adds that package to `immersive.full` in Android 9's `policy_control` global setting
+  (system user only; elsewhere it is disabled) and, off, removes just that entry; it shows what the
+  setting holds. On the emulator: policy_control hid the status bar of another app and its content
+  took the space; the switch wrote and removed its entry and left an existing one alone. Not tried
+  on the car: whether SAIC's top bar is the status bar, and whether CarPlay's picture grows or
+  leaves a black strip until the phone reconnects. Tyre pressure and accent colour now sit side by
+  side in the wide Settings layout, so the page still fits.
 - 2026-10-23 — App 2.19.1: "Foreground apps" card on the Logs tab, step 1 of the CarPlay
   full-screen experiment. It reads which apps came to the front in the last 30 minutes (usage
   events, open to the system user without a declared permission), the open tasks, the