chore: add CLAUDE.md with project guidelines

CLAUDE.md

@@ -0,0 +1,97 @@
+# KeyMapper
+
+## Project Overview
+
+Android app for custom key/gamepad remapping, macros, and on-screen buttons. Supports Android 8.0+ (minSdk 26), targets API 36. Distributed on Google Play and F-Droid (FOSS flavor).
+
+- **Package:** `io.github.sds100.keymapper`
+- **Languages:** Kotlin (primary), Rust (event device handling), C++ (system bridge JNI)
+
+## Build Commands
+
+```bash
+./gradlew assembleDebug       # debug APK
+./gradlew assembleCi          # CI build (minified)
+./gradlew assembleRelease     # release build (requires KEYSTORE_PASSWORD and KEY_PASSWORD env vars)
+./gradlew clean               # clean build outputs
+```
+
+## Test & Lint Commands
+
+```bash
+# Kotlin unit tests
+./gradlew testDebugUnitTest
+./gradlew :base:testDebugUnitTest   # single module
+
+# Kotlin lint
+./gradlew ktlintCheck         # check
+./gradlew ktlintFormat        # auto-fix
+
+# Rust (run from evdev/src/main/rust/evdev_manager)
+cargo fmt --check
+cargo test --package evdev_manager_core
+```
+
+CI runs all of the above on every PR (see `.github/workflows/pull-request.yml`).
+
+## Architecture & Modules
+
+Multi-module Gradle project using MVVM, Hilt DI, Room, StateFlow/Flow, Jetpack Compose, and Coroutines.
+
+| Module | Responsibility |
+|---|---|
+| `app/` | Entry point: `MainActivity`, `KeyMapperApp`, `MyAccessibilityService` |
+| `base/` | UI screens and ViewModels (actions, constraints, triggers, keymaps, settings) |
+| `common/` | Shared utilities and models |
+| `data/` | Room database, repositories, DataStore, migrations |
+| `system/` | Device APIs, permission management |
+| `sysbridge/` | C++ JNI via CMake for elevated system access |
+| `evdev/` | Rust event device handling + JNI bindings |
+| `api/` | AIDL public interface definitions |
+| `systemstubs/` | Mock stubs for system classes used in tests |
+
+Most business logic lives in `base/src/main/java/io/github/sds100/keymapper/`.
+
+## Code Style
+
+- **Kotlin:** ktlint with android_studio code style (configured via `.editorconfig`)
+  - No function expression bodies
+  - Trailing commas allowed
+  - Run `./gradlew ktlintFormat` before committing
+- **Rust:** `cargo fmt`
+
+## Commit Message Convention
+
+```
+#<issue_number> <type>: <description>
+```
+
+Types: `feat`, `fix`, `chore`, `refactor`, `style`
+
+Example: `#2025 feat: add button to report bug on home screen`
+
+## Compose Guidelines
+
+- `Modifier` is always the first parameter after required params
+- Use `LocalCustomColorsPalette` (not `MaterialTheme.colorScheme`) for non-standard colors
+- Check `KeyMapperIcons` before using other icon sources
+- Use `LocalUriHandler.openUriSafe` extension for URL launching — do not hoist URL launching logic up the call stack
+- Use import statements; never use fully qualified names in Compose code
+- Write `@Preview` composables for every screen
+
+## Adding a New Action (10-step checklist)
+
+First determine whether the action is editable. Then:
+
+1. Add a new ID to `ActionId`
+2. Create a new `ActionData` sealed class variant
+3. Map to/from entity in `ActionDataEntityMapper`
+4. Assign a category in `ActionUtils`
+5. If editable, add to `isEditable` in `ActionUtils`
+6. Add a title string in `strings.xml`
+7. Add title and Compose icon in `ActionUtils` (ignore drawables)
+8. Add title in `ActionUiHelper`
+9. Stub out execution in `PerformActionsUseCase`
+10. Handle creation in `CreateActionDelegate`
+
+Do not delete existing action code. Follow existing naming conventions exactly. Add new code near similar existing actions.