Initialize project skeleton with CLI and documentation

Add initial project structure including:
- Go module with Cobra CLI dependency
- Root command and main entrypoint
- Basic documentation (README, AGENTS.md, architecture, decisions,
  development, roadmap)
- Configuration example and gitignore
- Tool version management with mise
- Comprehensive project rules and conventions

README.md

@@ -0,0 +1,48 @@
+# MyGO
+
+MyGO is a WebDisk (cloud drive) server, written in Go.
+
+**Current status**: pre-alpha — project skeleton with no core functionality implemented yet.
+
+---
+
+## Roadmap
+
+### v0
+
+- [ ] CLI configuration management (`mygo config`)
+- [ ] User authentication (JWT)
+- [ ] File upload / download / management (HTTP API)
+- [ ] Admin endpoints
+- [ ] WebDAV support
+
+### Future
+
+- [ ] Image server
+- [ ] Pastebin & code snippet editing in sharing
+- [ ] S3 storage backend
+- [ ] Nextcloud-compatible API
+
+---
+
+## CLI
+
+`mygo` is the backend entrypoint with these subcommands:
+
+| Command | Description |
+|---------|-------------|
+| `mygo serve` | Start the backend server |
+| `mygo config` | Manage instance configuration |
+| `mygo status` | Show server status |
+
+---
+
+## Frontend
+
+The frontend uses React + TypeScript and communicates with the backend via HTTP API. Frontend source is maintained in a separate repository.
+
+---
+
+## Development
+
+See `docs/development.md` for build and test workflows. See `AGENTS.md` for behavioral conventions.