Add Copilot instructions for repository

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+# Copilot Instructions for Nitrite Database
+
+## Project Overview
+
+Nitrite Database is an open source embedded NoSQL database for Java. It's a multi-module Maven project that supports both in-memory and file-based persistent storage.
+
+**Key Features:**
+- Embedded, serverless document store
+- Document-oriented with schema-less collections
+- Extensible storage engines (MVStore, RocksDB)
+- Full-text search and indexing
+- Transaction support
+- Android compatibility (API Level 24+)
+
+## Repository Structure
+
+This is a multi-module Maven project with the following modules:
+
+- `nitrite` - Core database module
+- `nitrite-bom` - Bill of materials for dependency management
+- `nitrite-jackson-mapper` - Jackson-based JSON mapper
+- `nitrite-mvstore-adapter` - MVStore storage adapter
+- `nitrite-rocksdb-adapter` - RocksDB storage adapter
+- `nitrite-spatial` - Spatial indexing support
+- `nitrite-support` - Support utilities
+- `nitrite-native-tests` - GraalVM native image tests
+- `potassium-nitrite` - Kotlin extension
+
+## Development Environment
+
+### Java Versions
+- **Minimum supported:** Java 11 (as configured in pom.xml)
+- **Primary testing:** Java 11 and 17
+- **Native image testing:** Java 17 and 21 with GraalVM
+
+### Build Tool
+Maven is the build tool. Key commands:
+
+```bash
+# Build the project
+mvn clean install
+
+# Build without tests
+mvn clean install -DskipTests
+
+# Run tests only
+mvn test
+
+# Build specific module
+mvn -pl nitrite clean install
+```
+
+## Code Guidelines
+
+### Java Standards
+1. **Minimum compatibility:** Code must compile and run on Java 11 (as per maven.compiler.source=11 in pom.xml)
+2. **Code style:** Follow existing code formatting in the repository (see `.editorconfig`)
+3. **Dependencies:** Check `pom.xml` files before adding new dependencies
+4. **API changes:** Be cautious with public API changes - this is a library used by others
+
+### Testing Requirements
+1. **Always run tests:** Execute `mvn test` before submitting changes
+2. **Write tests:** New features should include unit tests
+3. **Test coverage:** Maintain or improve code coverage (tracked via CodeCov)
+4. **Cross-platform:** Consider Linux, macOS, and Windows compatibility
+
+### Module-Specific Guidelines
+- When modifying storage adapters (`nitrite-mvstore-adapter`, `nitrite-rocksdb-adapter`), ensure compatibility with the core module
+- Changes to `nitrite` core module may require updates to adapter modules
+- Kotlin extension (`potassium-nitrite`) should mirror Java API capabilities
+
+## Pull Request Best Practices
+
+### Before Creating a PR
+1. Run full build: `mvn clean install`
+2. Ensure all tests pass across Java 11 and 17
+3. Check for compilation warnings
+4. Update documentation if changing public APIs
+5. Add or update tests for your changes
+
+### PR Scope
+- Keep PRs focused on a single issue or feature
+- Include issue references in PR description
+- Document breaking changes clearly
+- Update CHANGELOG.md for significant changes
+
+### Review Process
+- All PRs require review before merging
+- CI must pass (build on Linux, macOS, Windows)
+- CodeQL security analysis must pass
+- Code coverage should not decrease significantly
+
+## Security Considerations
+
+1. **No secrets in code:** Never commit API keys, passwords, or credentials
+2. **Input validation:** Validate all user inputs, especially in query operations
+3. **File operations:** Be careful with file I/O operations in storage adapters
+4. **Dependencies:** Check for known vulnerabilities in dependencies
+5. **CodeQL:** Address any CodeQL security findings
+
+## Common Tasks
+
+### Good Tasks for Copilot
+- Bug fixes in specific modules
+- Adding unit tests to improve coverage
+- Documentation updates (JavaDoc, README)
+- Code style and formatting improvements
+- Refactoring isolated methods/classes
+- Adding new query operators or filters
+- Implementing feature requests with clear specifications
+
+### Tasks Requiring Human Review
+- Breaking API changes
+- Changes to core database engine logic
+- Modifications to transaction handling
+- Storage format changes
+- Security-sensitive operations
+- Multi-module architectural changes
+
+## Documentation
+
+- **JavaDoc:** All public APIs must have JavaDoc comments
+- **README updates:** Update README.md if changing features or usage
+- **User guide:** Major features may need documentation at https://nitrite.dizitart.com
+- **Code comments:** Add comments for complex logic, not obvious code
+
+## Gradle vs Maven
+This project uses **Maven**, not Gradle. All build commands should use `mvn`.
+
+## Related Projects
+
+- **Potassium Nitrite:** Kotlin extension within this repository
+- **Nitrite Flutter:** Separate repository for Flutter/Dart version
+- **Deprecated:** Nitrite DataGate and Nitrite Explorer (no longer maintained)
+
+## Communication
+
+- **Issues:** Use GitHub issues for bugs and feature requests
+- **Discussions:** Use GitHub Discussions for questions and community interaction
+- **Contributing:** See CONTRIBUTING.md for detailed contribution guidelines
+
+## Additional Resources
+
+- **Website:** https://nitrite.dizitart.com
+- **Documentation:** https://nitrite.dizitart.com/java-sdk/getting-started/index.html
+- **API Docs:** https://javadoc.io/doc/org.dizitart/nitrite
+- **GitHub:** https://github.com/nitrite/nitrite-java