Adds AGENT.md file

Change-Id: I48a83b0c2557a977e08f299a752564514a8b5f8e

Author: JoseAlcerreca

AGENT.md

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+# Now in Android Project
+
+Now in Android is a native Android mobile application written in Kotlin. It provides regular news
+about Android development. Users can choose to follow topics, be notified when new content is
+available, and bookmark items.
+
+## Architecture
+
+This project is a modern Android application that follows the official architecture guidance from Google. It is a reactive, single-activity app that uses the following:
+
+-   **UI:** Built entirely with Jetpack Compose, including Material 3 components and adaptive layouts for different screen sizes.
+-   **State Management:** Unidirectional Data Flow (UDF) is implemented using Kotlin Coroutines and Flows. ViewModels act as state holders, exposing UI state as streams of data.
+-   **Dependency Injection:** Hilt is used for dependency injection throughout the app, simplifying the management of dependencies and improving testability.
+-   **Navigation:** Navigation is handled by Jetpack Navigation 2 for Compose, allowing for a declarative and type-safe way to navigate between screens.
+-   **Data:** The data layer is implemented using the repository pattern.
+    -   **Local Data:** Room and DataStore are used for local data persistence.
+    -   **Remote Data:** Retrofit and OkHttp are used for fetching data from the network.
+-   **Background Processing:** WorkManager is used for deferrable background tasks.
+
+## Modules
+The main Android app lives in the `app/` folder. Feature modules live in "feature/" and core and shared modules in "core/".
+
+## Commands to Build & Test
+
+The app and Android libraries have two product flavors: `demo` and `prod`.
+
+- Build: `./gradlew assemble{Variant}`. Typically `assembleDemoDebug`.
+- Fix linting/formatting: `./gradlew --init-script gradle/init.gradle.kts spotlessApply`
+- Run local tests: `./gradlew {variant}Test`
+- Run single test: `./gradlew {variant}Test --tests "com.example.myapp.MyTestClass"`
+- Run local screenshot tests: `./gradlew verifyRoborazziDemoDebug`
+
+### Instrumented tests
+
+- Gradle-managed devices to run on device tests: `./gradlew pixel6api31aospDebugAndroidTest`. Also `pixel4api30aospatdDebugAndroidTest` and `pixelcapi30aospatdDebugAndroidTest`.
+
+### Creating tests
+
+#### Instrumented tests
+
+- Tests for UI features should only use ComposeTestRule with a ComponentActivity.
+- Bigger tests live in :app and they can start activities like MainActivity.
+
+#### Local tests
+
+- Kotlinx Coroutines for most assertions
+- Turbine for complex coroutine tests
+- Truth for assertions
+
+## Continuous integration
+
+- The workflows are defined in `.github/workflows/*.yaml` and they contain various checks.
+- Screenshot tests are generated by CI, so they shouldn't be checked into the repo from a workstation.
+
+## Version control and code location
+
+- The project uses git and is hosted in github.com/android/nowinandroid.