Add justfile wrapping the Nix flake build/dev/deps tasks

Encodes the two flake gotchas: ?submodules=1 (submodule sources) and
--builders '' (build locally instead of copying the SDK closure to nixbuild).

justfile

@@ -0,0 +1,45 @@
+# moonlight-android — task runner (https://github.com/casey/just)
+#
+# Wraps the Nix flake (devShell + hermetic nonRoot debug APK build). Two flake
+# gotchas are baked in so `just <recipe>` just works:
+#   * `?submodules=1` — the build needs the moonlight-common-c + enet submodule
+#     sources, which Nix only includes when the flake is fetched with submodules.
+#   * `--builders ""` — force a LOCAL build. Without it the Android SDK/NDK
+#     closure (multi-GB) gets copied to the remote builder (eu.nixbuild.net),
+#     which is far slower than building here where the SDK is already realised.
+
+pkg := ".?submodules=1#moonlight-android"
+build_flags := "--builders '' --print-build-logs"
+
+# list available recipes
+default:
+    @just --list
+
+# enter the dev shell (JDK 17 + Android SDK 34 / NDK 27 + Gradle), then e.g. ./gradlew assembleNonRootDebug
+dev:
+    nix develop '.?submodules=1'
+
+# build the nonRoot debug APK -> ./result/app-nonRoot-debug.apk
+build:
+    nix build '{{ pkg }}' {{ build_flags }}
+
+# build and print the resulting APK path
+apk: build
+    @ls -l result/app-nonRoot-debug.apk
+
+# install the built debug APK onto a connected device/emulator (needs adb + USB debugging)
+install: build
+    nix run nixpkgs#android-tools -- adb install -r result/app-nonRoot-debug.apk
+
+# regenerate the offline Maven lockfile (deps.json) after changing dependencies
+deps:
+    nix build '.?submodules=1#moonlight-android.mitmCache.updateScript'
+    ./result
+
+# evaluate the flake without building (catches eval errors fast)
+check:
+    nix flake check '.?submodules=1' --no-build
+
+# remove the build result symlink
+clean:
+    rm -f result