A promise that resolves once the server is listening.
Remarks
Startup validates HTTP credential mode, creates the runtime-neutral MCP
pipeline, listens on the resolved port, and installs SIGTERM/SIGINT graceful
shutdown handlers. Request handling remains per-request and stateless for the
current MCP HTTP protocol.
Throws
CredentialResolutionError when the selected HTTP credential mode is
not configured safely.
Start the hardened Streamable HTTP MCP transport.