Covers the rustup requirement (Homebrew rust can't cross-compile to
Android), env vars needed for cargo tauri android build, install via
adb, and the cleartext-traffic gotcha for release builds against ws://
rosbridge endpoints.
The .app bundle's binary doesn't auto-update on rebuild without tauri-cli
(not installed on the dev machine) — document the manual sync step so a
fresh clone doesn't hit the "changes aren't showing up" trap.
Dongubak