Fix Android release APK crash: enable new architecture for RN 0.84

The release APK was crashing with "TurboModuleRegistry.getEnforcing(...):
'PlatformConstants' could not be found" because newArchEnabled was set to
false while MainApplication.kt uses bridgeless/new-arch APIs
(loadReactNative, getDefaultReactHost). RN 0.84 requires new arch enabled
for core TurboModules like PlatformConstants to be registered.

- Enable newArchEnabled=true in gradle.properties (default for RN 0.84)
- Pass -PnewArchEnabled=false only for Detox Android builds which need old arch

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: gre

example/.detoxrc.js

@@ -19,7 +19,8 @@ module.exports = {
     'android.debug': {
       type: 'android.apk',
       binaryPath: 'android/app/build/outputs/apk/debug/app-debug.apk',
-      build: 'cd android && ./gradlew assembleDebug assembleAndroidTest',
+      build:
+        'cd android && ./gradlew assembleDebug assembleAndroidTest -PnewArchEnabled=false',
       testBinaryPath:
         'android/app/build/outputs/apk/androidTest/debug/app-debug-androidTest.apk',
       reversePorts: [8081],

example/android/gradle.properties

@@ -32,8 +32,7 @@ reactNativeArchitectures=armeabi-v7a,arm64-v8a,x86,x86_64
 # your application. You should enable this flag either if you want
 # to write custom TurboModules/Fabric components OR use libraries that
 # are providing them.
-# Temporarily disabled for Detox E2E testing compatibility
-newArchEnabled=false
+newArchEnabled=true
 
 # Use this property to enable or disable the Hermes JS engine.
 # If set to false, you will be using JSC instead.