chg: add copilot instructions

Author: nicokant

.github/copilot-instructions.md

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+# Copilot Instructions for nina-maps
+
+## Architecture Overview
+
+This is a React map editor for geospatial data using MapLibre GL. The architecture follows a configuration-driven approach where map definitions are JSON files validated against Zod schemas.
+
+**Key data flow:** JSON config → Zod validation → Zustand store → transformation libs → MapLibre/DeckGL layers
+
+## Schemas (src/schemas/)
+
+All types are defined as Zod schemas and exported from `src/schemas/index.ts` via `src/types.ts`. When modifying types:
+
+1. Edit the Zod schema in the appropriate file under `src/schemas/`
+2. Run `pnpm generate-schema` to regenerate `schemas/map-config.schema.json`
+3. Types are auto-inferred - never manually duplicate type definitions
+
+Schema organization:
+- `legend/` - Raster (linear, interval, image) and vector (fill, line, circle) legends
+- `source/` - Layer sources: pmtiles, titiler, raster, parquet, wms, wmts
+- `layer/` - Layer, Folder, Tree structures
+- `map.ts` - MapConfig, MapSettings, ViewState
+
+## State Management (src/hooks/app.ts)
+
+Global state uses Zustand with immer middleware. The store (`useAppStore`) holds the entire MapConfig and provides actions for mutations.
+
+**Pattern:** Use reselect selectors (`createAppSelector`) for derived data. Export custom hooks like `useLayer(id)`, `useLayers()`, `useMaplibreMapConf()`.
+
+## Layer Transformation (src/libs/)
+
+- `toMaplibre.ts` - Converts layer configs to MapLibre source/layer specs. Contains `buildPMTilesLayer()`, `buildRasterLayer()`, etc.
+- `toDeckGL.ts` - Converts parquet layers to DeckGL layers with GeoArrow support
+
+When adding a new layer type: add schema in `src/schemas/source/`, export from `src/schemas/source/index.ts`, add builder function in `toMaplibre.ts`.
+
+## Routing (src/routes/)
+
+Uses TanStack Router with file-based routing:
+- `$mapId.tsx` - Dynamic map routes
+- `editor/` - Editor-specific routes with `_layout` for shared layout
+- `_view/` folders contain read-only views, `edit/` contains editable forms
+
+Routes use `createFileRoute()` and can define loaders with TanStack Query via `queryOptions()`.
+
+## Components
+
+- `src/components/layer-fields/` - Form fields for each source type (PMTilesFields, TitilerFields, etc.)
+- `src/components/form-items/` - Reusable form primitives with TanStack Form
+- `MaplibreMap.tsx` - Main map component, integrates Popup for feature info
+
+## Commands
+
+```bash
+pnpm dev              # Development server (proxies /titiler to localhost:8989)
+pnpm build            # Production build with TypeScript check
+pnpm lint             # Biome check
+pnpm lint:fix         # Biome auto-fix
+pnpm generate-schema  # Regenerate JSON schema from Zod definitions
+```
+
+## Code Style
+
+- Use `@/` path alias for imports from `src/` (configured in tsconfig.app.json and vite.config.ts)
+- Biome for formatting (2-space indent, 120 line width) - run `pnpm lint:fix`
+- JSDoc comments for exported functions, especially in libs/
+
+## Adding New Source Types
+
+1. Create schema file: `src/schemas/source/newtype.ts`
+2. Export from `src/schemas/source/index.ts` and add to `LayerConfigSchema` union
+3. Add form fields: `src/components/layer-fields/NewTypeFields.tsx`
+4. Add transformation: `src/libs/toMaplibre.ts` (or `toDeckGL.ts` for DeckGL layers)
+5. Run `pnpm generate-schema`