Studio's /v1/chat/completions silently stripped standard OpenAI `tools`
and `tool_choice` fields, so clients using standard function calling
(opencode, Claude Code, Cursor, Continue, ...) never got structured
tool_calls back. Adds a client-side pass-through path mirroring the
existing Anthropic /v1/messages flow: when `tools` is present without
Studio's `enable_tools` shorthand, the request is forwarded to
llama-server verbatim so the client sees native id, finish_reason
("tool_calls"), delta.tool_calls, and accurate usage tokens.
Also wires Anthropic tool_choice forwarding: /v1/messages previously
accepted tool_choice on the request model but silently dropped it with
a warning. Translate the four Anthropic shapes to OpenAI format and
forward them so agentic clients can actually enforce tool use.
- ChatCompletionRequest: add tools, tool_choice, stop; extra="allow"
- ChatMessage: accept role="tool", optional tool_call_id / tool_calls /
name; content is now optional (assistant with only tool_calls)
- routes/inference.py: _openai_passthrough_stream /
_openai_passthrough_non_streaming helpers, routing branch in
openai_chat_completions, vision+tools via content-parts injection
- _build_passthrough_payload: tool_choice parameter (default "auto")
- anthropic_compat: anthropic_tool_choice_to_openai() translator
- tests/test_openai_tool_passthrough.py: Pydantic + translator unit tests
- tests/test_studio_api.py: 5 new E2E tests (non-stream, stream,
multi-turn, OpenAI SDK, Anthropic tool_choice=any regression)