Add comprehensive GitHub Copilot instructions for development workflow

.github/copilot-instructions.md

@@ -0,0 +1,109 @@
+# unplugin-vue-router
+File-based routing plugin for Vue Router with TypeScript support. A build-time plugin that simplifies routing setup by automatically generating routes from your file structure.
+
+Always reference these instructions first and fallback to search or bash commands only when you encounter unexpected information that does not match the info here.
+
+## Working Effectively
+- Install dependencies and build the repository:
+  - `npm install -g pnpm` -- Install pnpm if not available (required package manager)
+  - `pnpm install --frozen-lockfile` -- takes 3 minutes. NEVER CANCEL. Set timeout to 5+ minutes.
+  - `pnpm run build` -- takes 7 seconds. Build both core and runtime using tsdown.
+- `pnpm run vitest --coverage run` -- takes 9 seconds. Run all tests with coverage.
+- `pnpm run lint` -- takes 3 seconds. Run Prettier formatting checks.
+- Run the playground (main validation method):
+  - `pnpm run play` -- Start development server at http://localhost:5173
+  - `pnpm run play:build` -- takes 4 seconds. Build playground for production.
+- Build documentation:
+  - `pnpm run docs:build` -- takes 33 seconds. NEVER CANCEL. Set timeout to 60+ minutes.
+  - `pnpm run docs` -- Start VitePress dev server for documentation.
+
+## Validation
+- Always run `pnpm run play` and test the playground after making changes. The playground demonstrates file-based routing functionality with example routes.
+- ALWAYS run through complete test scenarios in the playground by:
+  1. Navigate to different routes (e.g., /users/123, /about, /nested/routes)
+  2. Test dynamic routes with parameters
+  3. Verify TypeScript route completions work in IDE
+  4. Check that new routes appear automatically from file structure
+- The playground includes comprehensive examples in `playground/src/pages/` including:
+  - Dynamic routes: `[id].vue`, `[...path].vue`
+  - Nested routes in folders
+  - Layout routes with parentheses: `(group).vue`
+  - Custom route definitions with `<route>` blocks
+- Always run `pnpm run lint` and fix any formatting issues before committing.
+- Run the full test suite `pnpm run test` for complete validation (includes build + test + docs).
+
+## Common Tasks
+
+### Build Commands
+- `pnpm run build:core` -- Build main library (tsdown)
+- `pnpm run build:runtime` -- Build runtime components (data loaders, volar plugins)
+- Build outputs to `dist/` folder with CommonJS and ESM formats
+
+### Test Commands  
+- `pnpm run vitest` -- Run tests in watch mode with UI
+- `pnpm run dev` -- Alias for vitest UI mode
+- Tests include unit tests (*.spec.ts) and type tests (*.test-d.ts)
+
+### Repository Structure
+```
+src/
+├── core/           # Main routing logic (tree building, route generation)
+├── codegen/        # Code generation for routes and types
+├── data-loaders/   # Data loading functionality (experimental)
+├── volar/          # Vue language server integrations  
+├── utils/          # Shared utilities
+├── index.ts        # Main entry point
+├── runtime.ts      # Runtime exports
+├── vite.ts         # Vite plugin entry
+├── webpack.ts      # Webpack plugin entry
+├── rollup.ts       # Rollup plugin entry
+└── esbuild.ts      # esbuild plugin entry
+
+playground/         # Development playground with example routes
+docs/              # VitePress documentation
+examples/          # Example projects (Nuxt integration)
+e2e/              # End-to-end tests
+tests/            # Test utilities and mocks
+```
+
+### Key Files to Check After Changes
+- Always check `src/core/tree.ts` after modifying route tree logic
+- Check `src/codegen/generateRouteRecords.ts` after changing route generation
+- Test playground at `playground/src/pages/` for route behavior changes
+- Update route schema `route.schema.json` if adding new route options
+
+### Package Manager
+- Uses **pnpm** (version 10.14.0+) - NOT npm or yarn
+- Workspace setup with playground and examples as separate packages
+- Lockfile: `pnpm-lock.yaml` (commit changes to this file)
+
+### TypeScript Configuration
+- Main config: `tsconfig.json`
+- Build uses `tsdown` (not tsc) for better performance
+- Path aliases configured for internal module resolution
+- Vue compiler options included for SFC support
+
+### CI Requirements
+The GitHub Actions workflow will fail if:
+- Prettier formatting is incorrect (`pnpm run lint`)
+- Build fails (`pnpm run build`) 
+- Tests fail (`pnpm run vitest`)
+- Playground build fails (`pnpm run -C playground build`)
+- Documentation build fails (`pnpm run docs:build`)
+
+## Important Notes
+- **NEVER CANCEL** any build or test command - they may take several minutes but should complete
+- The playground is your primary validation tool - always test changes there
+- Warning about "Language ts for &lt;route&gt; is not supported" is expected and harmless
+- Routes are generated automatically from file structure in pages directories
+- TypeScript definitions are generated at build time
+- Data loaders feature is experimental and subject to change
+- Always use the exact timeout values provided to avoid premature cancellation
+
+## Common Validation Scenarios
+After making changes, validate by:
+1. **Route Generation**: Add a new `.vue` file in `playground/src/pages/` and verify it appears in routing
+2. **Dynamic Routes**: Test routes with parameters like `[id].vue` work correctly  
+3. **TypeScript**: Check that route names and params have proper type completion
+4. **Build**: Ensure `pnpm run build` succeeds and outputs to `dist/`
+5. **Plugin Integration**: Test Vite plugin works in playground development mode