feat(nix): enable Android emulator and system images in dev shell

Enable local AVD testing by including emulator and Google APIs system images (x86_64) in the Nix-managed Android SDK. Inline the intermediate androidComposition variable into androidSdk for clarity. Reformat input attributes and align shellHook output spacing.

flake.nix

@@ -6,9 +6,13 @@
     flake-utils.url = "github:numtide/flake-utils";
   };
 
-  outputs = { self, nixpkgs, flake-utils }:
-    flake-utils.lib.eachDefaultSystem (system:
-      let
+  outputs = {
+    self,
+    nixpkgs,
+    flake-utils,
+  }:
+    flake-utils.lib.eachDefaultSystem (
+      system: let
         pkgs = import nixpkgs {
           inherit system;
           config = {
@@ -18,7 +22,7 @@
         };
 
         buildToolsVersion = "35.0.0";
-        androidComposition = pkgs.androidenv.composeAndroidPackages {
+        androidSdk = (pkgs.androidenv.composeAndroidPackages {
           # Command-line & platform tools
           cmdLineToolsVersion = "11.0";
           platformToolsVersion = "35.0.2";
@@ -29,9 +33,11 @@
           # Target platforms (36 required by AGP 9.0.1 / compileSdk 36)
           platformVersions = ["36" "35" "34"];
 
-          # For the emulator
-          includeEmulator = false;
-          includeSystemImages = false;
+          # Emulator + system images for local AVD testing
+          includeEmulator = true;
+          includeSystemImages = true;
+          systemImageTypes = ["google_apis"];
+          abiVersions = ["x86_64"];
 
           # NDK (not needed for this project, but handy)
           includeNDK = false;
@@ -47,17 +53,14 @@
             "intel-android-sysimage-license"
             "mips-android-sysimage-license"
           ];
-        };
-
-        androidSdk = androidComposition.androidsdk;
-
+        }).androidsdk;
       in {
         devShells.default = pkgs.mkShell {
           buildInputs = with pkgs; [
             # Java 21 (required for AGP 9.x / Gradle 9.x)
             jdk21
 
-            # Android SDK (platforms, build-tools, platform-tools)
+            # Android SDK (platforms, build-tools, platform-tools, emulator, system-images)
             androidSdk
 
             # Kotlin compiler