docs: add CLAUDE.md for Claude Code context

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project
+
+OpenCut is a privacy-first browser-based video editor. Bun monorepo with Turborepo.
+
+## Commands
+
+```bash
+bun install                    # Install dependencies
+bun dev:web                    # Dev server (Next.js + Turbopack, port 3000)
+bun build:web                  # Production build
+bun lint:web                   # Lint with Biome
+bun lint:web:fix               # Lint and auto-fix
+bun test                       # Run tests (bun test)
+bun dev:ws-bridge              # WebSocket bridge server (port 3001)
+bun dev:mcp                    # MCP server
+
+# Database (requires Docker services running)
+docker compose up -d db redis serverless-redis-http
+cd apps/web && bun db:generate  # Generate Drizzle migrations
+cd apps/web && bun db:migrate   # Run migrations
+cd apps/web && bun db:push:local # Push schema to local DB
+```
+
+## Monorepo Structure
+
+- `apps/web/` - Next.js 16 app (main editor)
+- `packages/ui/` - Shared UI components (Iconify icons)
+- `packages/env/` - Zod-validated environment variables
+- `packages/ws-bridge/` - WebSocket bridge between MCP and browser
+- `packages/mcp-server/` - MCP server for AI assistant integration
+
+## Code Style
+
+- **Formatter/Linter:** Biome - tabs, double quotes, 80 char line width
+- **Comments:** Explain WHY, not WHAT. No obvious or changelog-style comments.
+- **File organization:** One file, one responsibility. Extract shared logic when a file exceeds ~500 lines or has multiple distinct concerns.
+- `lib/` is domain logic (specific to this app), `utils/` is generic helpers (portable to any project)
+
+## Architecture
+
+### EditorCore Singleton
+
+All editor state flows through a singleton `EditorCore` with specialized managers (playback, timeline, scene, project, media, renderer, command, save, audio, selection).
+
+- **In React components:** use the `useEditor()` hook from `@/hooks/use-editor` (subscribes to state changes, auto re-renders)
+- **Outside React:** use `EditorCore.getInstance()` directly
+
+### Actions System
+
+User-triggered operations go through the actions system. Source of truth: `@/lib/actions/definitions.ts`. Handlers registered in `@/hooks/use-editor-actions.ts`.
+
+In components, use `invokeAction("action-name")` rather than calling `editor.xxx()` directly (the action layer adds toasts, validation, etc.). Direct editor calls are for internal use (commands, tests, multi-step operations).
+
+### Commands (Undo/Redo)
+
+Commands in `@/lib/commands/` (organized by domain: timeline, media, scene, project). Each extends `Command` from `base-command.ts` with `execute()` and `undo()`.
+
+Pattern: Actions trigger Commands. Actions = "what triggered this", Commands = "how to do it and undo it".
+
+### State Management
+
+Zustand stores in `src/stores/` for UI state (editor, timeline, preview, panels, sounds, stickers, keybindings, assets-panel).
+
+## Tech Stack
+
+Next.js 16 (App Router + Turbopack), React 19, Tailwind CSS 4, Radix UI / shadcn, Drizzle ORM + PostgreSQL 17, Better Auth, Upstash Redis, Zustand, FFmpeg.js, WaveSurfer.js, Biome, Bun 1.2.18, Turborepo.
+
+## Database
+
+PostgreSQL 17 + Drizzle ORM. Schema at `apps/web/src/lib/db/schema.ts`. Docker Compose provides local Postgres, Redis, and serverless-redis-http.