/claim #275

Adds serve mode scaffolding:

• New flags: –serve, –serve-port
• Prints: “golem-cli running MCP Server at port {port}”
• Placeholder server enumerates CLI tools/resources and waits for Ctrl-C
• No MCP SDK integration yet; to follow in a separate PR once versions are aligned

Upstream: https://github.com/golemcloud/golem-cli