Add GitHub Copilot instructions for ArcaneChat Android

Co-authored-by: adbenitez <24558636+adbenitez@users.noreply.github.com>

.github/copilot-instructions.md

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+# GitHub Copilot Instructions for ArcaneChat Android
+
+## Project Overview
+
+ArcaneChat is a Delta Chat Android client built on top of the official Delta Chat client with several improvements. It is a messenger app that uses email infrastructure for secure communication.
+
+**Technology Stack:**
+- **Language:** Java (Java 8 compatibility)
+- **Build System:** Gradle with Android Gradle Plugin 8.11.1
+- **Min SDK:** 21 (Android 5.0)
+- **Target SDK:** 35 (Android 15)
+- **NDK Version:** 27.0.12077973
+- **Native Components:** Rust (deltachat-core-rust submodule)
+- **UI Framework:** Android SDK, Material Design Components
+- **Testing:** JUnit 4, Espresso, Mockito, PowerMock, AssertJ
+
+## Repository Structure
+
+- `src/main/` - Main application source code
+- `src/androidTest/` - Instrumented tests (UI tests, benchmarks)
+- `src/gplay/` - Google Play flavor-specific code
+- `src/foss/` - F-Droid/FOSS flavor-specific code
+- `jni/deltachat-core-rust/` - Native Rust core library (submodule)
+- `scripts/` - Build and helper scripts
+- `docs/` - Documentation
+- `fastlane/` - App store metadata and screenshots
+
+## Build Instructions
+
+### Prerequisites
+
+1. **Initialize submodules:**
+   ```bash
+   git submodule update --init --recursive
+   ```
+
+2. **Build native libraries:**
+   ```bash
+   scripts/ndk-make.sh
+   ```
+   Note: First run may take significant time as it builds for all architectures (armeabi-v7a, arm64-v8a, x86, x86_64)
+
+3. **Build APK:**
+   ```bash
+   ./gradlew assembleDebug
+   ```
+
+### Build Flavors
+
+- **gplay:** Google Play version with Firebase Cloud Messaging (applicationId: `com.github.arcanechat`)
+- **foss:** F-Droid version without proprietary services (applicationId: `chat.delta.lite`)
+
+### Build Outputs
+
+- Debug APKs: `build/outputs/apk/gplay/debug/` and `build/outputs/apk/fat/debug/`
+- Release APKs require signing configuration in `~/.gradle/gradle.properties`
+
+## Testing
+
+### Running Unit Tests
+
+```bash
+./gradlew test
+```
+
+### Running Instrumented Tests
+
+1. **Disable animations** on your device/emulator:
+   - Developer Options → Set "Window animation scale", "Transition animation scale", and "Animator duration scale" to 0x
+
+2. **Run tests:**
+   ```bash
+   ./gradlew connectedAndroidTest
+   ```
+
+### Online Tests
+
+Some tests require real email credentials. Configure in `~/.gradle/gradle.properties`:
+```properties
+TEST_ADDR=youraccount@yourdomain.org
+TEST_MAIL_PW=yourpassword
+```
+
+### UI Tests and Benchmarks
+
+- Located in `src/androidTest/java/com/b44t/messenger/`
+- Test categories: `uitests/online/`, `uitests/offline/`, `uibenchmarks/`
+- Run via Android Studio: Run → Edit Configurations → Android Instrumented Test
+
+## Coding Conventions
+
+### General Guidelines
+
+1. **Embrace existing style:** Match the coding style of the file you're editing
+2. **Minimize changes:** Don't refactor or rename in the same PR as bug fixes/features
+3. **Readable over paradigmatic:** Favor readability over strict Java patterns
+4. **Avoid premature optimization:** Keep things simple and on point
+5. **No excessive abstraction:** Avoid unnecessary factories, one-liner functions, or abstraction layers
+6. **Comments:** Only add comments if they match existing style or explain complex logic
+
+### Architecture
+
+- **UI/Model Separation:** Delta Chat Core (Rust) handles the model layer
+- **High-level interface:** Core provides data in UI-ready form; avoid additional transformations in UI layer
+- **Direct approach:** Prefer direct implementation over excessive class hierarchies
+
+### Key Principles
+
+- Work hard to avoid options and up-front choices
+- Avoid speaking about keys/encryption in primary UI
+- App must work offline and with poor network
+- Users don't read much text
+- Consistency matters
+- Primary UI should only show highly useful features
+
+## Common Development Tasks
+
+### Adding New Features
+
+1. Consider the UX philosophy (minimal options, offline-first, simplicity)
+2. Check if core library changes are needed before implementing in UI
+3. Match existing code style in modified files
+4. Add instrumented tests for UI changes when appropriate
+5. Update relevant documentation
+
+### Modifying Core Integration
+
+- Core library is in `jni/deltachat-core-rust/` submodule
+- Java bindings are in `src/main/java/com/b44t/messenger/Dc*.java`
+- JSON-RPC bindings in `chat.delta.rpc.*` package (generated via dcrpcgen)
+
+### Working with Translations
+
+- Translations managed via Transifex (not in repository)
+- English source strings: `res/values/strings.xml`
+- Don't mix string changes with refactoring
+
+### Debugging Native Code
+
+Decode crash symbols:
+```bash
+$ANDROID_NDK_ROOT/ndk-stack --sym obj/local/armeabi-v7a --dump crash.txt > decoded.txt
+```
+
+## WebXDC Support
+
+ArcaneChat has extended WebXDC support:
+- `window.webxdc.arcanechat` - Version detection
+- `sendToChat()` - Extra properties: `subject`, `html`, `type` (sticker/image/audio/video/file)
+- External link support in apps
+- `manifest.toml` - `orientation` field for landscape mode
+
+## Important Files
+
+- `build.gradle` - Main build configuration
+- `CONTRIBUTING.md` - Contribution guidelines
+- `BUILDING.md` - Detailed build setup
+- `RELEASE.md` - Release process
+- `proguard-rules.pro` - ProGuard configuration
+- `google-services.json` - Firebase configuration (gplay flavor)
+
+## Package Structure
+
+- `org.thoughtcrime.securesms.*` - Main UI components (legacy namespace from Signal)
+- `com.b44t.messenger.*` - Delta Chat core integration
+- `chat.delta.rpc.*` - JSON-RPC bindings (generated)
+
+## Notes for AI Assistants
+
+- This is a fork of Delta Chat Android with ArcaneChat-specific improvements
+- Maintain compatibility with Delta Chat core library
+- Test on both gplay and foss flavors when making changes
+- Native library must be rebuilt after core changes
+- ProGuard is enabled in both debug and release builds
+- Multi-dex is enabled due to app size