feat: implement modular installation system

引入模块化安装系统,支持可配置的工作流组合:

核心改进:
- .claude-plugin/marketplace.json: 移除废弃模块引用,精简插件清单
- .gitignore: 添加 Python 开发环境忽略项(.venv, __pycache__, .coverage)
- Makefile: 标记 make install 为 LEGACY,推荐使用 install.py
- install.sh: codex-wrapper 安装脚本,添加到 PATH

新架构使用 config.json 控制模块启用/禁用,支持:
- 选择性安装工作流(dev/bmad/requirements/essentials)
- 声明式操作定义(merge_dir/copy_file/run_command)
- 版本化配置管理

迁移路径: make install -> python3 install.py --install-dir ~/.claude

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

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

install.sh

@@ -1,6 +1,13 @@
 #!/bin/bash
 set -e
 
+echo "⚠️  WARNING: install.sh is LEGACY and will be removed in future versions."
+echo "Please use the new installation method:"
+echo "  python3 install.py --install-dir ~/.claude"
+echo ""
+echo "Continuing with legacy installation in 5 seconds..."
+sleep 5
+
 # Detect platform
 OS=$(uname -s | tr '[:upper:]' '[:lower:]')
 ARCH=$(uname -m)