fix(android): testOptions isReturnDefaultValues = true

Unit tests touching Android framework statics (Bundle.EMPTY,
android.os.Bundle constructor in MediaItem/SessionCommand
construction) failed with NPE/ExceptionInInitializerError because
JVM unit tests run against android.jar's stub classes whose methods
throw "Method ... not mocked" by default. Enable
isReturnDefaultValues so stub methods return defaults — Bundle.EMPTY
ends up null and is fine because we just thread it through
SessionCommand without inspecting it.

Fixes LikeMediaCallbackTest's 5 failures on run #311. Lightweight —
no Robolectric, no androidTest. The first JVM-side test file in the
project to touch Android framework classes.

android/app/build.gradle.kts

@@ -80,6 +80,19 @@ android {
         buildConfig = true
     }
 
+    testOptions {
+        unitTests {
+            // JVM unit tests run against android.jar's stub methods,
+            // which throw `RuntimeException("Method ... not mocked")`
+            // when touched (including statics like Bundle.EMPTY).
+            // Return defaults instead so tests that pass Bundles
+            // through without inspecting them (e.g. SessionCommand
+            // construction in LikeMediaCallbackTest) just work,
+            // without dragging in Robolectric.
+            isReturnDefaultValues = true
+        }
+    }
+
     packaging {
         resources.excludes +=
             setOf(