docs: update CLAUDE.md with comprehensive project guidance

- Add project architecture section describing cat chat simulator
- Document Ink-based terminal UI technology stack
- Add chat UI design patterns (Static component, loading states)
- Document cat behavior and UX patterns
- Update file structure to reflect TSX entry point
- Add local testing command and development notes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: koki-develop

CLAUDE.md

@@ -8,32 +8,53 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 - **Lint**: `bun run lint` - Runs Biome linter checks
 - **Format**: `bun run fmt` - Formats code using Biome with unsafe fixes
 - **Type check**: `bun run typecheck` - Runs TypeScript compiler without emitting files
+- **Test locally**: `bun run ./dist/index.js` - Run the built CLI locally
 
-## Project Structure
+## Project Architecture
 
-This is a TypeScript CLI tool using the following stack:
+This is a terminal-based chat UI CLI tool that simulates a conversation with a cat. The architecture consists of:
+
+### Core Components
+- **CLI Entry Point** (`src/index.tsx`): Commander.js setup that renders the Ink app
+- **Chat Application** (`src/App.tsx`): React-based terminal UI using Ink framework
+- **Build System** (`scripts/build.ts`): Custom Bun build script that creates executable CLI binary
+
+### Technology Stack
 - **Runtime**: Bun (primary development runtime)
 - **CLI Framework**: Commander.js for argument parsing
+- **Terminal UI**: Ink (React for CLIs) with community components:
+  - `ink-text-input` for user input
+  - `ink-spinner` for loading states
 - **Build Tool**: Custom Bun build script that creates executable CLI binary
 - **Linting/Formatting**: Biome (replaces ESLint + Prettier)
 - **Package Manager**: Bun with lockfile management
 
-### Key Files
-- `src/index.ts` - Main entry point with Commander.js CLI setup
-- `scripts/build.ts` - Custom build script that outputs to `dist/` with shebang
-- `biome.json` - Biome configuration for linting and formatting
-- `tsconfig.json` - TypeScript configuration optimized for bundler mode
+### Chat UI Design Patterns
+- **Message Persistence**: Uses Ink's `<Static>` component to render chat history that doesn't re-render
+- **Loading States**: Displays spinner with "Thinking..." during cat response delay
+- **Input Management**: Disables cursor and prevents duplicate submissions during loading
+- **Cat Behavior**: Always responds with "ﾆｬｰ" after a 500ms delay to simulate thinking
 
 ### Build Process
 The build process creates a standalone executable CLI tool:
 1. Removes existing `dist/` directory
-2. Uses Bun.build() to bundle TypeScript to JavaScript
+2. Uses Bun.build() to bundle TypeScript/TSX to JavaScript
 3. Adds Node.js shebang for CLI execution
 4. Makes output executable with chmod +x
 
+### Key Files
+- `src/index.tsx` - Main entry point with Commander.js CLI setup (TSX for JSX support)
+- `src/App.tsx` - Main chat UI component with React hooks and Ink components
+- `scripts/build.ts` - Custom build script that outputs to `dist/` with shebang
+- `biome.json` - Biome configuration for linting and formatting
+- `tsconfig.json` - TypeScript configuration optimized for bundler mode with JSX support
+
 ## Development Notes
 
+- Entry point is TSX (not TS) to support JSX syntax for Ink components
 - Uses `"module": "Preserve"` and `"moduleResolution": "bundler"` in tsconfig for modern bundler compatibility
 - Biome is configured with strict rules including unused variable/import detection
 - Package is configured as ESM with `"type": "module"`
-- Binary is published as `cat-code` command via `bin` field in package.json
+- Binary is published as `cat-code` command via `bin` field in package.json
+- Message state uses simple array with auto-incrementing IDs (length + 1/2)
+- Color scheme: cyan for user messages, green for cat messages, yellow for prompt