chore: add vitest config, CLAUDE.md, and gitignore .claude/

.gitignore

@@ -19,6 +19,7 @@ coverage/
 .idea/
 .vscode/
 *.swp/
+.claude/
 
 # env
 .env

CLAUDE.md

@@ -0,0 +1,49 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Consentify is a minimal, headless cookie consent management SDK. It's a TypeScript monorepo with zero runtime dependencies, designed for SSR-safe usage in modern web frameworks.
+
+## Commands
+
+```bash
+# Install dependencies
+pnpm install
+
+# Build all packages
+pnpm -r build
+
+# Build core only
+pnpm -w --filter @consentify/core build
+```
+
+## Publishing
+
+CI publishes on tags matching `core-v*`:
+```bash
+pnpm changeset           # Create changeset
+pnpm changeset version   # Version packages
+git tag core-v1.0.0 && git push origin core-v1.0.0  # Trigger release
+```
+
+## Architecture
+
+### Core Package (`packages/core`)
+
+Single-file SDK (`src/index.ts`) built around `createConsentify()` factory that returns separate `client` and `server` APIs:
+
+- **Server API**: Reads/writes consent via raw `Cookie` headers (Node.js compatible)
+- **Client API**: Browser-side storage with React `useSyncExternalStore` support via `subscribe()` and `getServerSnapshot()`
+
+Key design patterns:
+- Policy versioning via hash - consent invalidates when categories change
+- `'necessary'` category is always `true` and cannot be disabled
+- Storage abstraction supports cookie (canonical) and localStorage (optional mirror)
+- State uses discriminated union: `{ decision: 'unset' }` | `{ decision: 'decided', snapshot }`
+
+### Internal utilities
+- `fnv1a()` / `stableStringify()` - deterministic policy hashing
+- `readCookie()` / `writeCookie()` - isomorphic cookie handling
+- Listener pattern for React reactivity (`listeners` Set, `syncState`, `notifyListeners`)

vitest.config.ts

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+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+    test: {
+        environment: 'happy-dom',
+        include: ['packages/*/src/**/*.test.ts'],
+    },
+});