feat(audience-sdk): enable Android build target on sample app (SDK-294)

- Add Android to includePlatforms in both Runtime asmdefs so the SDK
  compiles when building for Android (was Standalone/macOS/Windows only)
- Set scriptingBackend=IL2CPP and AndroidTargetArchitectures=ARMv7+ARM64
  in the sample's ProjectSettings
- Add Audience.Editor assembly with AndroidManifestPostProcessor
  (IPostGenerateGradleAndroidProject) to inject android.permission.INTERNET
  — SDK uses HttpClient not UnityWebRequest so Unity won't auto-add it
- Add AndroidBuilder.cs to the sample for batchmode -executeMethod builds
- Extend ScriptingBackendOverride to support BuildTargetGroup.Android
- Ignore src/Packages/Audience/README.md.meta (non-asset, no GUID value)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: nattb8

.gitignore

@@ -19,6 +19,7 @@
 *.DotSettings.user.meta
 Directory.Build.props.meta
 Directory.Build.targets.meta
+src/Packages/Audience/README.md.meta
 
 # MemoryCaptures can get excessive in size.
 # They also could contain extremely sensitive data

examples/audience/Assets/Editor/AndroidBuilder.cs

@@ -0,0 +1,60 @@
+#nullable enable
+
+using System;
+using UnityEditor;
+using UnityEngine;
+
+namespace Immutable.Audience.Samples.SampleApp.Editor
+{
+    // Invoked by CI via:
+    //   Unity -batchmode -buildTarget Android \
+    //         -executeMethod Immutable.Audience.Samples.SampleApp.Editor.AndroidBuilder.Build \
+    //         -quit
+    //
+    // Optional CLI arg:
+    //   --buildPath <path>   Output path for the APK (default: Builds/Android/audience.apk)
+    internal static class AndroidBuilder
+    {
+        private const string DefaultBuildPath = "Builds/Android/audience.apk";
+
+        public static void Build()
+        {
+            string buildPath = GetArgValue("--buildPath") ?? DefaultBuildPath;
+
+            var options = new BuildPlayerOptions
+            {
+                scenes = new[] { "Assets/SampleApp/Scenes/SampleApp.unity" },
+                locationPathName = buildPath,
+                target = BuildTarget.Android,
+                targetGroup = BuildTargetGroup.Android,
+                options = BuildOptions.None,
+            };
+
+            Debug.Log($"[AndroidBuilder] Building APK → {buildPath}");
+
+            var report = BuildPipeline.BuildPlayer(options);
+            var summary = report.summary;
+
+            if (summary.result == UnityEditor.Build.Reporting.BuildResult.Succeeded)
+            {
+                Debug.Log($"[AndroidBuilder] Build succeeded ({summary.totalSize / 1024 / 1024} MB).");
+            }
+            else
+            {
+                Debug.LogError($"[AndroidBuilder] Build failed: {summary.totalErrors} error(s).");
+                EditorApplication.Exit(1);
+            }
+        }
+
+        private static string? GetArgValue(string flag)
+        {
+            var args = Environment.GetCommandLineArgs();
+            for (int i = 0; i < args.Length - 1; i++)
+            {
+                if (args[i] == flag)
+                    return args[i + 1];
+            }
+            return null;
+        }
+    }
+}

examples/audience/Assets/Editor/AndroidBuilder.cs.meta

@@ -18,9 +18,11 @@ namespace Immutable.Audience.Samples.SampleApp.Editor
     //   Mono   → Disabled (Mono studios rarely strip; High under Mono can
     //                      strip Net.Http SSL chain code paths).
     //
+    // Supported targets: Standalone, Android.
+    //
     // Usage:
     //   AUDIENCE_SCRIPTING_BACKEND=Mono2x Unity -batchmode -runTests ...
-    //   AUDIENCE_SCRIPTING_BACKEND=IL2CPP Unity -batchmode -runTests ...
+    //   AUDIENCE_SCRIPTING_BACKEND=IL2CPP Unity -batchmode -buildTarget Android ...
     //
     // Unset means "respect ProjectSettings.asset as-is".
     internal sealed class ScriptingBackendOverride : IPreprocessBuildWithReport
@@ -42,12 +44,15 @@ public void OnPreprocessBuild(BuildReport report)
                     $"{EnvVar} must be 'IL2CPP' or 'Mono2x'; got '{requested}'"),
             };
 
-            var group = BuildTargetGroup.Standalone;
+            var group = report.summary.platformGroup;
+            if (group != BuildTargetGroup.Standalone && group != BuildTargetGroup.Android)
+                return;
+
             var currentBackend = PlayerSettings.GetScriptingBackend(group);
             if (currentBackend != backend)
             {
                 PlayerSettings.SetScriptingBackend(group, backend);
-                Debug.Log($"[{nameof(ScriptingBackendOverride)}] backend {currentBackend} → {backend}.");
+                Debug.Log($"[{nameof(ScriptingBackendOverride)}] {group} backend {currentBackend} → {backend}.");
             }
 
             var stripping = backend == ScriptingImplementation.IL2CPP
@@ -57,7 +62,7 @@ public void OnPreprocessBuild(BuildReport report)
             if (currentStripping != stripping)
             {
                 PlayerSettings.SetManagedStrippingLevel(group, stripping);
-                Debug.Log($"[{nameof(ScriptingBackendOverride)}] managedStrippingLevel {currentStripping} → {stripping}.");
+                Debug.Log($"[{nameof(ScriptingBackendOverride)}] {group} managedStrippingLevel {currentStripping} → {stripping}.");
             }
         }
     }