Only the env helper needs a per-shell variant, since it has to mutate the
calling shell; android-setup.sh is executed rather than sourced and already
works from fish.
The fish version finds NDK/JDK candidates via `find` rather than globs because
fish raises an error on a wildcard matching nothing, and "SDK with no ndk/
directory yet" is a normal state the helper has to report cleanly.
Also switch the bash helper's NDK selection to `find | sort -V` so the two
agree: glob order is lexicographic, which would rank 9.x above 10.x. Verified
both pick the same NDK and JDK on this machine and against a fixture with
9.0.111 / 10.0.222 / 28.2.333 / 30.0.999-beta2 installed.
scripts/android-env.sh exports ANDROID_HOME/NDK_HOME/JAVA_HOME by
auto-detection, so there are no machine-specific paths to keep in sync. It
skips prerelease NDKs when several are installed and prefers Android Studio's
bundled JDK 21, which Gradle accepts.
Also document that Android Studio must be launched via
`cargo tauri android dev --open` rather than by opening src-tauri/gen/android
directly: Studio's Run button delegates the Rust build to
`tauri android android-studio-script`, which reads the dev-server address from
/tmp/<identifier>-server-addr and fails with "missing addr file" if no Tauri
dev session is running. `cargo tauri android build` needs no addr file.
