Expose Windows process creation flags on the shared command wrapper and use
`CREATE_NO_WINDOW` when launching local stdio MCP servers, including fallback
launches without Job Object containment. Preserve `CREATE_SUSPENDED` when
assigning the server to a Job Object before execution.
Add a Windows regression test covering direct launches and launches through
`cmd.exe`. Verify that the server has no console, initializes successfully,
returns tools, and exits after shutdown.
GitOrigin-RevId: 84475e82999d91a431e09327d4f5639b59c01427