feat: Add experimental MCP tools integration for enhanced codebase analysis

## New Features
- **MCP Tools Integration**: Added support for Model Context Protocol tools
  - Exa MCP Server: External API patterns and best practices
  - Code Index MCP: Advanced internal codebase search and indexing
- **Enhanced Workflow Planning**: Updated pre_analysis to include MCP tool steps
- **Documentation Updates**: Added MCP tool setup guides and usage examples

## Changes
### Core Components
- Updated `plan.md` with MCP integration principles and implementation approach guidelines
- Added MCP tool steps in pre_analysis workflow: `mcp_codebase_exploration`, `mcp_external_context`
- Enhanced context accumulation with external best practices lookup

### Documentation
- Added comprehensive MCP tools section in both English and Chinese README
- Updated installation requirements and integration guidelines
- Added GitHub repository links for required MCP servers

### Agent Enhancements
- Updated multiple agents to support MCP tool integration
- Enhanced context gathering capabilities with external pattern analysis

## Technical Details
- MCP tools provide faster analysis through direct codebase indexing
- Automatic fallback to traditional bash/CLI tools when MCP unavailable
- Enhanced pattern recognition and similarity detection capabilities

🧪 **Experimental**: MCP integration is currently experimental and optional

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

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

.claude/agents/general-purpose.md

@@ -31,6 +31,7 @@ You are a versatile execution specialist focused on completing high-quality task
 ### 1. Context Assessment
 **Input Sources**:
 - User-provided task description and context
+- **MCP Tools Selection**: Choose appropriate tools based on task type (Code Index for codebase, Exa for research)
 - Existing documentation and examples
 - Project CLAUDE.md standards
 - Domain-specific requirements