Add a fish version of the Android env helper

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.

README.md

@@ -145,9 +145,16 @@ Every Android command needs `ANDROID_HOME` / `NDK_HOME` / `JAVA_HOME`. Source
 the helper once per shell — it auto-detects all three:
 
 ```bash
-source scripts/android-env.sh
+source scripts/android-env.sh      # bash / zsh
 ```
 
+```fish
+source scripts/android-env.fish    # fish
+```
+
+Only the env helper is shell-specific (it has to mutate the calling shell);
+`android-setup.sh` is executed rather than sourced, so it works from any shell.
+
 Then, from the project root:
 
 ```bash

scripts/android-env.fish

@@ -0,0 +1,89 @@
+#!/usr/bin/env fish
+#
+# android-env.fish — export the environment the Android build needs (fish shell).
+#
+# SOURCE this, don't execute it:
+#
+#   source scripts/android-env.fish
+#   cargo tauri android dev --open
+#
+# bash/zsh users want scripts/android-env.sh instead — only the *env* script is
+# shell-specific, since it has to mutate the calling shell. ./scripts/android-setup.sh
+# is executed rather than sourced, so it already works from any shell.
+#
+# Everything is auto-detected, so there are no machine-specific paths to keep in
+# sync. Run ./scripts/android-setup.sh first to install the pieces.
+
+function _mtgc_android_env
+    # --- SDK ---
+    set -l sdk $HOME/Android/Sdk
+    if set -q ANDROID_HOME; and test -n "$ANDROID_HOME"
+        set sdk $ANDROID_HOME
+    end
+    if not test -d $sdk
+        echo "android-env: no Android SDK at $sdk (run ./scripts/android-setup.sh)" >&2
+        return 1
+    end
+
+    # --- NDK: newest *stable* installed (skip beta/rc/canary) ---
+    # `find` rather than a glob: fish raises an error on a wildcard that matches
+    # nothing, and an SDK with no ndk/ directory at all is a normal state here.
+    # `sort -V` so 9.x doesn't outrank 10.x the way plain lexicographic would.
+    set -l ndk ""
+    for d in (find $sdk/ndk -mindepth 1 -maxdepth 1 -type d 2>/dev/null | sort -V)
+        set -l rev (sed -n 's/^Pkg.Revision *= *//p' $d/source.properties 2>/dev/null)
+        switch "$rev"
+            case '*beta*' '*rc*' '*canary*'
+                continue
+        end
+        set ndk $d
+    end
+    if test -z "$ndk"
+        echo "android-env: no stable NDK under $sdk/ndk (run ./scripts/android-setup.sh)" >&2
+        return 1
+    end
+
+    # --- JDK: Gradle/AGP reject very new JDKs; prefer Studio's bundled JBR 21 ---
+    # Ordered by preference; globbed locations go through `find` for the same
+    # unmatched-wildcard reason as above.
+    set -l studio $HOME/.local/share/JetBrains/Toolbox/apps/android-studio
+    set -l candidates \
+        $studio/jbr \
+        (find $studio -mindepth 2 -maxdepth 2 -type d -name jbr 2>/dev/null | sort -V) \
+        $HOME/android-studio/jbr \
+        /opt/android-studio/jbr \
+        (find /usr/lib/jvm -maxdepth 1 -name 'java-21-openjdk*' 2>/dev/null | sort -V) \
+        (find /usr/lib/jvm -maxdepth 1 -name 'java-17-openjdk*' 2>/dev/null | sort -V)
+
+    set -l jdk ""
+    for d in $candidates
+        # Test for javac specifically: a JRE-only or leftover-empty directory
+        # under /usr/lib/jvm must not count.
+        if test -x $d/bin/javac
+            set jdk $d
+            break
+        end
+    end
+    if test -z "$jdk"
+        echo "android-env: no JDK 21/17 found (Gradle rejects the system default)" >&2
+        return 1
+    end
+
+    set -gx ANDROID_HOME $sdk
+    set -gx NDK_HOME $ndk
+    set -gx JAVA_HOME $jdk
+    # adb/emulator live here; harmless if already present.
+    if not contains $sdk/platform-tools $PATH
+        set -gx PATH $sdk/platform-tools $PATH
+    end
+
+    echo "ANDROID_HOME=$ANDROID_HOME"
+    echo "NDK_HOME=$NDK_HOME"
+    echo "JAVA_HOME=$JAVA_HOME"
+end
+
+_mtgc_android_env
+set -l _mtgc_ok $status
+functions -e _mtgc_android_env
+# Leave the sourced file's exit status reflecting whether detection succeeded.
+test $_mtgc_ok -eq 0

scripts/android-env.sh

@@ -21,14 +21,15 @@ _mtgc_android_env() {
     fi
 
     # --- NDK: newest *stable* installed (skip beta/rc/canary) ---
+    # `sort -V` so 9.x doesn't outrank 10.x the way plain lexicographic would.
     local best=""
-    for d in "$sdk"/ndk/*; do
-        [ -d "$d" ] || continue
+    while IFS= read -r d; do
+        [ -n "$d" ] || continue
         case "$(sed -n 's/^Pkg.Revision *= *//p' "$d/source.properties" 2>/dev/null)" in
             *beta*|*rc*|*canary*) continue ;;
         esac
         best="$d"
-    done
+    done < <(find "$sdk/ndk" -mindepth 1 -maxdepth 1 -type d 2>/dev/null | sort -V)
     ndk="$best"
     if [ -z "$ndk" ]; then
         echo "android-env: no stable NDK under $sdk/ndk (run ./scripts/android-setup.sh)" >&2