docs: fix docstrings across public API surface (#2095)

src/mcp/client/sse.py

@@ -47,6 +47,7 @@ async def sse_client(
         headers: Optional headers to include in requests.
         timeout: HTTP timeout for regular operations (in seconds).
         sse_read_timeout: Timeout for SSE read operations (in seconds).
+        httpx_client_factory: Factory function for creating the HTTPX client.
         auth: Optional HTTPX authentication handler.
         on_session_created: Optional callback invoked with the session ID when received.
     """