One Qt/QML launcher for macOS and Windows with a pluggable game backend:
- android (macOS): upstream's Google Play sign-in, version checks and the
  mcpelauncher engine, kept intact behind a new shell.
- windows: finds Minecraft for Windows / Minecraft Preview (GDK and Store
  builds), starts it through its minecraft: URI and tracks when it runs.

Shared features, identical on both platforms:
- Worlds: list with game mode, size and last played (from level.dat),
  automatic backups after each play session, manual backups, restore as a
  new world, .mcworld import and export, move to Trash.
- Packs: resource, behavior and skin packs; .mcpack/.mcaddon import that
  updates packs in place by uuid.
- New design system in the AL-Arcade brand: theme tokens, restyled
  controls, Lucide icons, Inter + IBM Plex Sans Arabic, voxel logo, icon
  and hero art generated from code (tools/brand), RTL-aware layout.

macOS:
- Native WebKit Google sign-in sheet and Xbox/error helpers in Swift,
  replacing QtWebEngine (424 MB of the upstream app).
- The credentials key moves from the settings file to the Keychain.
- scripts/build-macos.sh builds engine + launcher + helpers into a signed
  .app/.dmg and records the real minimum macOS of the bundled libraries.

Windows:
- Credential Manager secret store, crash handler, icon/version resources,
  manifest; cross-compiles on macOS with llvm-mingw and Qt 6.11.2
  (scripts/fetch-windows-toolchain.sh, cmake/toolchains).

Upstream fixes: the Google Play ToS approval window was never opened; the
token cache is now keyed on startup so cached tokens survive restarts.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>