Add custom port/address parameter to --mcp flag with optional value support

[Copilot]

The --mcp flag only enabled MCP mode, requiring users to modify config.yaml to change the listening port.

Changes

• Flag type: Changed --mcp to support optional values using custom flag implementation
• Optional value support: --mcp alone uses config.yaml default port (backward compatible)
• Formats supported:
  • --mcp uses config.yaml default (e.g., port 8080)
  • --mcp=:8080 specifies custom port (short format, auto-expands to http://localhost:8080)
  • --mcp=http://localhost:8080 specifies full URL
  • --mcp=http://0.0.0.0:8080 specifies custom host with port
• Implementation: Custom mcpFlag type implementing IsBoolFlag() interface for optional value behavior
• Field additions: Added MCPServerSet field to track if flag was explicitly set
• Priority: Command-line parameter overrides config.yaml when specified

Usage

# Use config.yaml default port (NEW - addresses feedback)
./enscan --mcp

# Custom port with short format (requires = syntax)
./enscan --mcp=:9999

# Full URL with custom host (requires = syntax)
./enscan --mcp=http://0.0.0.0:8080

# Omit flag entirely to use normal mode
./enscan -n 小米

The implementation uses strings.HasPrefix for safe string handling, validates addresses through the existing utils.ExtractPortString function, and implements Go's IsBoolFlag() interface to support optional values.

Testing

• ✅ --mcp without value uses config.yaml default port
• ✅ --mcp=:PORT custom port format works correctly
• ✅ --mcp=http://... full URL format works correctly
• ✅ All comprehensive integration tests pass
• ✅ Code review feedback addressed
• ✅ Security scan: 0 vulnerabilities found

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>

<agent_instructions>mcp参数支持自定义</agent_instructions>

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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[keac]

未配置端口号情况下指定默认端口

[Copilot]

未配置端口号情况下指定默认端口

已实现。现在 --mcp 单独使用时会使用配置文件中的默认端口（如 http://localhost:8080），也可以通过 --mcp=:8080 或 --mcp=http://localhost:9999 指定自定义端口。

实现于提交 60ae379 和 45c2fc9。

用法示例：

• ./enscan --mcp - 使用配置文件默认值
• ./enscan --mcp=:9999 - 使用自定义端口 9999
• ./enscan --mcp=http://0.0.0.0:8080 - 使用完整地址