Improve readability of CLI help option

[Kludex]

You can try mcp run --help locally.

Now it looks like this:

❯ mcp run --help
                                                                                                                                                                                 
 Usage: mcp run [OPTIONS] FILE_SPEC                                                                                                                                              
                                                                                                                                                                                 
 Run a MCP server.                                                                                                                                                               
 The server can be specified in two ways:                                                                                                                                        
 1. Module approach: server.py - runs the module directly, expecting a server.run() call.                                                                                        
 2. Import approach: server.py:app - imports and runs the specified server object.                                                                                               
                                                                                                                                                                                 
 Note: This command runs the server directly. You are responsible for ensuring all dependencies are available.                                                                   
 For dependency management, use `mcp install` or `mcp dev` instead.                            

[Kludex]

Btw, the import approach should have been server:app instead of adding the .py in it, as uvicorn does.