Add Copilot instructions for repository

.github/copilot-instructions.md

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+# ObjectQL - Copilot Instructions
+
+This is a TypeScript-based monorepo for ObjectQL, a universal data query engine designed to bridge MongoDB (schema-less) and PostgreSQL (schema-strict) with a unified JSON-DSL protocol. The project is AI-native and designed for LLM integration.
+
+## Code Standards
+
+### Required Before Each Commit
+- Ensure all TypeScript code compiles without errors
+- Run tests for packages you modified
+- Follow existing code structure and patterns in the monorepo
+
+### Development Flow
+- **Install dependencies**: `npm install`
+- **Build all packages**: `npm run build` (runs TypeScript compiler with project references)
+- **Test all packages**: `npm run test` (runs Jest tests across workspaces)
+- **Test specific package**: `npm run test --workspace=@objectql/core`
+- **Dev server**: `npm run dev` (starts @objectql/server in development mode)
+
+## Repository Structure
+
+This is a monorepo managed by npm workspaces:
+
+- `packages/core`: The query engine, AST parser, and metadata definitions
+- `packages/metadata`: Metadata type definitions and validation
+- `packages/driver-mongo`: MongoDB driver implementation
+- `packages/driver-knex`: SQL driver (PostgreSQL, MySQL, SQLite) using Knex with JSONB strategy
+- `packages/api`: API layer and query handling
+- `packages/server`: Server implementation
+- `packages/ui`: UI components
+- `packages/better-auth`: Authentication utilities
+- `examples/`: Usage examples and demonstrations
+- `docs/`: VitePress documentation site
+
+## Key Guidelines
+
+1. **Follow TypeScript best practices**
+   - Use strict type checking
+   - Export types from package index files
+   - Maintain existing type definitions
+
+2. **Maintain monorepo structure**
+   - Each package has its own `package.json`, `tsconfig.json`, and `jest.config.js`
+   - Use workspace protocol (`"@objectql/metadata": "*"`) for internal dependencies
+   - Root `tsconfig.json` uses project references for incremental builds
+
+3. **Write comprehensive tests**
+   - Place tests in `test/` directory within each package
+   - Use naming pattern `*.test.ts` for test files
+   - Use Jest as the testing framework with `ts-jest` preset
+   - Standard Jest config in each package: preset `ts-jest`, testEnvironment `node`, testMatch pattern `**/test/**/*.test.ts`
+   - Every new feature must include test cases
+
+4. **Follow metadata specifications**
+   - Maintain strict specification for Object Definitions
+   - See `docs/specifications/metadata.md` for details
+   - Object definitions use `.object.yml` files with YAML format
+
+5. **Preserve AI-native design**
+   - Queries are JSON ASTs, not string concatenation
+   - Maintain the unified JSON-DSL protocol across drivers
+   - Keep the abstraction layer between DSL and driver implementations
+
+6. **Documentation**
+   - Update relevant documentation in `docs/` when making significant changes
+   - Use VitePress for documentation: `npm run docs:dev` to preview
+
+## Architecture Principles
+
+- **Dual-Stack Engine**: Support both MongoDB (via native driver) and SQL databases (via Knex)
+- **Pluggable Architecture**: Core logic is decoupled from storage drivers
+- **Zero Heavy Dependencies**: Keep the project lightweight and modern
+- **Promise-based async API**: All async operations use Promises, not callbacks