llama_server: allow streaming tool use

[khimaros]

5ire, the most recommended open source MCP client requires streaming and tool use.

however, llama_server doesn't allow this:

llama.cpp/examples/server/utils.hpp

Line 565 in f17a3bb

throw std::runtime_error("Cannot use tools with stream");

it would be great to be able to use this tool with llama.cpp directly.

[unclemusclez]

this is also a requirement for OpenAI Codex
llama-server[1090]: got exception: {"code":500,"message":"Cannot use tools with stream","type":"server_error"}