Add copilot instructions

.github/copilot-instructions.md

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+This document provides explicit instructions for Copilot Agent to follow when working with this
+repository. It outlines the coding standards, project structure, and best practices to ensure
+high-quality contributions that align with the repository's goals and maintainability standards.
+
+## Repository Overview
+
+This repository is organized as a **monorepo** containing multiple applications and libraries. The
+main directories are:
+
+- `apps/` – Contains all application projects (e.g., browser, cli, desktop, web). Each app is
+  self-contained with its own configuration, source code, and tests.
+- `libs/` – Contains shared libraries and modules used across multiple apps. Libraries are organized
+  by domain or functionality (e.g., common, ui, platform, key-management).
+
+**Strict boundaries** must be maintained between apps and libraries. Do not introduce
+cross-dependencies that violate the intended modular structure. Always consult and respect the
+dependency rules defined in `eslint.config.mjs`, `nx.json`, and other configuration files.
+
+## Coding Standards and Best Practices
+
+### 1. Linting and Formatting
+
+- All code **must** pass ESLint and Prettier checks before being committed.
+- Use the provided configuration files (`eslint.config.mjs`, `.prettierrc`, etc.).
+- **Do not** override or disable linting/formatting rules unless explicitly instructed by repository
+  maintainers.
+- Run linting and formatting tools locally before submitting changes.
+
+### 2. TypeScript Usage
+
+- Use **strict typing** throughout the codebase. Avoid the use of `any` unless absolutely necessary
+  and justified with a comment.
+- Adhere to the settings in `tsconfig.json` and `tsconfig.eslint.json`.
+- Prefer interfaces and type aliases for type definitions. Use enums and literal types where
+  appropriate.
+- Always annotate function return types and exported members.
+
+### 3. Project Structure and File Organization
+
+- Place all source code for apps in their respective `src/` directories within `apps/`.
+- Place all source code for libraries in their respective `src/` directories within `libs/`.
+- Tests should be located in alongside the code in `*.spec.ts` files, following the conventions of
+  each app or library.
+- Do not place unrelated files or code in shared directories.
+- Keep configuration files (e.g., `jest.config.js`, `tsconfig.json`) at the root of each app or
+  library.
+
+### 4. Testing
+
+- All new features and bug fixes **must** include appropriate unit and/or integration tests.
+- Use Jest for unit tests.
+- Ensure all tests pass before submitting changes.
+- Write clear, descriptive test names and use test coverage tools to ensure code is well-tested.
+
+### 5. Commit Messages
+
+- Use the **conventional commit** format for all commits. Example:
+  `feat(browser): add autofill support for new form type`.
+- Prefix commits with `feat`, `fix`, `chore`, `docs`, `test`, `refactor`, etc., as appropriate.
+- Include a clear, concise description of the change and reference related issues when applicable.
+
+### 6. Security
+
+- **Never** commit secrets, credentials, or sensitive information. Follow the guidelines in
+  `SECURITY.md`.
+- Review code for potential security vulnerabilities, especially when handling authentication,
+  encryption, or user data.
+- Use environment variables and secure storage for sensitive configuration.
+
+### 7. Documentation
+
+- Update `README.md` or other relevant documentation files when making significant changes, adding
+  new features, or modifying existing behavior.
+- Document public APIs, exported functions, and complex logic with clear comments and docstrings.
+- Maintain up-to-date usage instructions and examples for each app and library.
+
+### 8. Dependency Management
+
+- Use `npm` for installing and managing dependencies. Do not use `yarn` or other package managers
+  unless specified.
+- Do not add or update any dependencies unless explicitly asked.
+- Do not modify `package.json` or `package-lock.json` unless required for the task.
+- Only the root `package.json` should be modified for adding new dependencies.
+
+### 9. Configuration and Tooling
+
+- Respect all configuration files at the root and within each app/library (e.g.,
+  `eslint.config.mjs`, `jest.config.js`, `tsconfig.json`).
+- Do not override or duplicate configuration unless required for a specific app or library.
+- Use provided scripts in `package.json` for building, testing, and linting.
+
+### 10. Communication and Collaboration
+
+- For questions, clarifications, or proposing significant changes, refer to `CONTRIBUTING.md` or
+  contact the repository maintainers.
+- Open issues or pull requests with detailed descriptions and context.
+- Review and address feedback promptly.
+
+## Summary Checklist for Copilot Agent
+
+- [ ] Respect monorepo structure and boundaries
+- [ ] Pass all linting and formatting checks
+- [ ] Use strict TypeScript typing
+- [ ] Add/update tests for all changes
+- [ ] Follow conventional commit messages
+- [ ] Do not commit secrets or sensitive data
+- [ ] Update documentation as needed
+- [ ] Use npm for dependencies and do not modify lockfiles unnecessarily
+- [ ] Adhere to all configuration and tooling standards