Replace Copilot instructions with CLAUDE.md

Author: kyoshino

.github/copilot-instructions.md

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+# Sveltia CMS
+
+Modern, Git-based headless CMS, drop-in replacement for Netlify/Decap CMS. Svelte 5 (runes) with JavaScript, Vite 8, Vitest 4. ~710 source files, 255 test files, 7,200+ tests. Ships as a browser bundle (IIFE + ES module), loaded via CDN or npm.
+
+## Setup
+
+- **pnpm only** — npm will not work correctly with this project.
+- Node v26 (see `.nvmrc`).
+- Run `pnpm install` first, and again after any `package.json` change.
+
+## Commands
+
+```bash
+pnpm dev              # dev server with hot reload
+pnpm build             # production build -> package/dist/
+pnpm build:watch
+pnpm preview
+
+pnpm check             # run all checks below — do this before committing
+pnpm check:eslint
+pnpm check:prettier
+pnpm check:stylelint
+pnpm check:svelte
+pnpm check:oxlint
+pnpm check:cspell
+pnpm check:imports     # custom script, more accurate than standard unused-import tools
+pnpm check:audit
+
+pnpm test
+pnpm test:coverage
+
+pnpm format             # auto-fix Prettier formatting
+```
+
+## Architecture
+
+```
+src/lib/
+├── components/     # Svelte UI (app.svelte is the root component)
+│   ├── assets/     # asset management UI
+│   └── contents/   # content editing UI
+├── services/       # business logic & data
+│   ├── app/            # core app services
+│   ├── assets/
+│   ├── api/               # api client wrappers
+│   ├── backends/        # GitHub/GitLab/Gitea integrations
+│   ├── config/           # CMS config handling
+│   ├── contents/         # content & collection management
+│   ├── integrations/     # external services
+│   ├── search/            # content search
+│   ├── user/              # auth & preferences
+│   └── utils/
+├── types/          # JSDoc/TS type definitions
+├── locales/        # i18n
+└── main.js         # entry point
+```
+
+Key config: `vite.config.js`, `svelte.config.js` (runes enabled), `jsconfig.json` (`$lib/*` alias), `eslint.config.js` (flat config, Airbnb + Svelte), `.prettierrc.yaml`, `.stylelintrc.yaml`.
+
+Build output: `package/dist/sveltia-cms.js` (IIFE), `package/dist/sveltia-cms.mjs` (ESM), full npm package in `package/`.
+
+## CI
+
+`.github/workflows/tests.yml` runs on every push: Check, Test, Build in parallel, using `.nvmrc` Node version and pnpm. A PR must pass ESLint, Prettier, all tests, Svelte compiler checks, the production build, and the unused-imports check.
+
+## Conventions
+
+- Style: Airbnb JS guide + project overrides in `eslint.config.js`. Single quotes in JS, double quotes in YAML/CSS. 100-char line length. Trailing commas always. Import order (builtin → external → internal → `$lib`) is enforced by ESLint.
+- Types: JSDoc comments (TypeScript-flavoured), centralized in `src/types/*.js`, imported via `@import`.
+- Svelte 5: runes syntax only — no legacy Svelte patterns. Use the Svelte MCP server / `svelte-file-editor` agent for any `.svelte` or `.svelte.js`/`.svelte.ts` work.
+- Prose: Canadian English in Markdown, American English in code/comments. Curly quotes in prose, straight quotes in source, backticks for inline code.
+- Tests: Vitest, co-located `*.test.js` files. Coverage tracked for `src/lib/{components,services}/**/*.js`; keep it at 100%. Use `sed` to spot uncovered lines in coverage reports.
+- Bundle size: stay under 2 MB. Current build is ~1.96 MB — close to the ceiling, so watch new dependencies carefully.
+- Target: modern browsers (ES2025).
+
+```javascript
+// import order
+import { get } from 'svelte/store';           // external
+
+import { cmsConfig } from '$lib/services/config';        // internal, $lib alias
+import Button from '$lib/components/common/button.svelte';
+
+/**
+ * @import { CmsConfig } from '$lib/types/public';
+ */
+```