Replace the honest stub with a working stdio<->streamable-HTTP MCP proxy:
connect upstream to COMFY_BRIDGE_URL as an HTTP MCP client, then run a
low-level stdio MCP server whose list_tools/call_tool forward to the
upstream session. Exits non-zero with a clear stderr message on connection
failure. Adds a real end-to-end round-trip test (boots the in-process
bridge on a free port, spawns the shim, drives it via a stdio MCP client).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
