Add --mcp-port flag for runtime port configuration

[Copilot]

User requested ability to specify MCP server listening port via command-line parameter instead of only through config file.

Changes

Flag & Configuration

• Added --mcp-port string flag in common/flag.go
• Added McpPort field to ENOptions struct in common/config.go

Port Selection Logic (runner/mcpServer.go)

• Command-line port takes precedence over config file
• Validates port range (1-65535) when specified via flag
• Config file fallback maintains backward compatibility

Documentation (README.md)

• Added usage examples for both default and custom port scenarios

Usage

# Use config file port (default: 8080)
./enscan --mcp

# Override with custom port
./enscan --mcp --mcp-port 9090

Port validation prevents invalid values at startup:

./enscan --mcp --mcp-port 99999
# Error: 无效的端口号: 99999 (端口号必须在 1-65535 之间)

Original prompt

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This section details on the original issue you should resolve

<issue_title>可以在--mcp地方加个参数指定监听到某个端口吗</issue_title>
<issue_description>可以在--mcp地方加个参数指定监听到某个端口吗</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 可以在--mcp地方加个参数指定监听到某个端口吗 #206

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