Cline rules for Expo

# Cline and Roo rules

Project rules for Cline and Roo Code in this Expo repository.
Use the project's commands. Do not invent a package manager, and do not run destructive shell commands.

## Tool use

- Read the files you will change before editing them.
- Prefer a focused patch over rewriting a whole file.
- Run the test command from this file after a behavior change, or say why you could not.
- Do not delete generated folders, lockfiles, or migrations unless the task says so.

## Stack

This repository is an Expo React Native app. JavaScript stays portable. Native modules are the ones Expo or the project already configured. Do not eject unless the task says to.

## Layout

- Screens live in the app or src directory the router already uses.
- Shared components stay presentation-only. Data hooks sit beside them.
- Platform-specific files use the `.ios` and `.android` suffixes the bundler already understands.

## Commands

- Dev: `npx expo start`
- Lint: `npm run lint`
- Tests: `npm test`

Use the script the repo already defines when it differs from the command above.

## Conventions

- Use the Expo SDK module that matches the installed SDK. Do not add a raw native library when an Expo module exists.
- Do not import Node built-ins into app code.
- Keep the navigation library the repo already uses.
- Handle the permission prompt the platform requires before using a sensor or the camera.
- Styles use StyleSheet or the utility system the project already has.
- Env vars that ship in the client are public. Treat them that way.

## Testing

Add or update tests when behavior changes.

Test hooks and pure logic in Jest. Do not require a device for a data-transform change.

## Style

- Optimize for the next reader over the shortest diff.
- Comment only when the why is non-obvious.
- Name things the way neighboring files already do.
- Do not reformat code you did not change.

## Errors

- Fail at the boundary. Do not swallow errors.
- Show a recoverable error state on the screen. Do not leave a rejected promise unhandled on launch.

## Scope

- Do the requested task. Do not refactor unrelated code.
- Match the rigor already in the repo. Fix what you touch.
- Ask one clarifying question only when the task cannot be finished without it. Otherwise state the assumption and continue.

## Avoid

- Do not call a native module at import time.
- Do not store secrets in app.json or an EXPO_PUBLIC_ variable.
- Do not upgrade the Expo SDK as a drive-by.
- Do not assume web, iOS, and Android share one bug.

## Done when

- The requested behavior works.
- The screen renders in Expo and `npm test` passes if the repo has tests.
- The diff stays inside the task.
- You list anything you could not run.