Fetch-based MCP client for this gateway's own /mcp endpoint (Streamable
HTTP). Same wire shape as the e2e helper in e2e/tests/mcp.spec.ts: one
JSON-RPC request per POST, a session id from initialize echoed back on
every later call, replies as plain JSON or a single SSE event.
Fetch-based MCP client for this gateway's own
/mcpendpoint (Streamable HTTP). Same wire shape as the e2e helper in e2e/tests/mcp.spec.ts: one JSON-RPC request per POST, a session id frominitializeechoed back on every later call, replies as plain JSON or a single SSE event.