docs: add AI instruction

Author: sushichan044

AGENTS.md

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+# AGENTS.md
+
+This file provides guidance to agents when working with code in this repository.
+
+## Repository Overview
+
+A monorepo for unified JavaScript/TypeScript toolchain configurations at VirtualLiveLab. Provides ESLint, Prettier, Stylelint, and TSConfig packages.
+
+## Development Commands
+
+```bash
+# Build
+pnpm run build                 # Build all packages
+pnpm run build:eslint          # Build eslint-config only
+pnpm run build:prettier        # Build prettier-config only
+pnpm run build:stylelint       # Build stylelint-config only
+
+# Test
+pnpm run test                  # Run all tests (Vitest)
+
+# Lint & Format
+pnpm run lint                  # Run ESLint
+pnpm run format                # Format code with Prettier
+
+# Release Flow
+pnpm run changeset             # Create changeset for version bump
+pnpm run release               # Build → Test → Publish (requires changeset)
+```
+
+## Repository Structure
+
+```
+packages/
+  ├── eslint-config/          # ESLint configuration
+  ├── prettier-config/        # Prettier configuration
+  ├── stylelint-config/       # Stylelint configuration
+  └── tsconfig/               # TypeScript configuration presets
+```
+
+- **Monorepo**: pnpm workspace
+- **Versioning**: Automatically managed with changesets
+- **Build tool**: tsdown (for each package)
+- **Test**: Vitest (snapshot tests)
+
+## Development Flow
+
+1. Fork and create a branch
+2. Make code changes
+3. Run `pnpm run build` to confirm no build errors
+4. Run `pnpm run changeset` to record changes
+   - Select the changed package(s)
+   - Choose version type (patch/minor/major)
+   - Describe the changes
+5. Create a PR
+6. After merge, GitHub Actions will automatically release
+
+## Technical Constraints
+
+- **Node.js**: >= 20 < 23
+- **Package Manager**: pnpm required (v10.18.0)
+- **Tool Management**: mise (run `mise setup` to set up environment)
+- **Commit Style**: Conventional Commits recommended
+
+## Testing
+
+Each package uses snapshot tests. When changing configurations, run `pnpm run test` to verify snapshots are updated correctly.

CLAUDE.md

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+AGENTS.md