chore: add AGENTS.md following agents.md standard (#180)

Co-authored-by: JounQin <8336744+JounQin@users.noreply.github.com>

Author: Copilot

AGENTS.md

@@ -0,0 +1,41 @@
+# AGENTS.md
+
+This monorepo contains the Doom documentation tool, export functionality, and related packages. Doom is a documentation generator built on top of Rspress.
+
+## Setup
+
+- Install dependencies: `yarn install`
+- Node.js 18.17.0+ (but not 20.0.0, use 20.1.0+)
+
+## Commands
+
+- **Build**: `yarn build` (clean and compile TypeScript)
+- **Clean**: `yarn clean` (clean TypeScript build artifacts)
+- **Dev**: `yarn dev` (development mode with file watching)
+- **Docs**: `yarn docs` (build and export docs) | `yarn docs:build` | `yarn docs:export`
+- **Format**: `yarn format` (format code with Prettier)
+- **Lint**: `yarn lint` (ESLint check)
+- **Serve**: `yarn serve` (serve built documentation)
+- **Test**: `yarn typecov` (type coverage check)
+- **Release**: `yarn release` (build and publish packages)
+- **Workspace**: `yarn workspaces list` (list packages) | `yarn workspace <name> <command>`
+
+## Code style
+
+- **Formatting**: Prettier configuration
+- **Types**: TypeScript strict mode
+- **Linting**: ESLint with project-specific rules
+- **Naming**: Follow existing patterns in the codebase
+
+## Architecture
+
+- **Structure**: Monorepo (Yarn workspaces)
+  - `packages/doom/`: Main documentation tool and CLI
+  - `packages/export/`: Document export functionality
+  - `docs/`: Project documentation
+  - `fixture-docs/`: Test documentation
+- **Testing**: Type coverage validation (`yarn typecov`)
+- **Configuration**:
+  - `doom.config.yml`: Main configuration
+  - `tsconfig.json`: TypeScript configuration
+  - `eslint.config.js`: Linting rules