Check for MITM-captured function calls BEFORE emitting text in the
streaming handler. This prevents the dummy 'Tool call completed'
placeholder (sent to the LS) from leaking to OpenCode, which was
confusing it into infinite loops.
Also removes duplicate function call storage at end of response loop
since they're now stored immediately when detected.
- Accept tools and tool_choice fields in CompletionRequest
- Convert OpenAI tools to Gemini format and store in MitmStore
- Detect MITM-captured function calls in streaming poll loop
- Emit tool_calls delta chunks in OpenAI streaming format
- Finish with 'tool_calls' reason instead of 'stop' when tools used
- Only clear tools when request has none (prevents stale state leak)
Tool definitions stored in MitmStore from /v1/responses requests were
persisting and getting injected into /v1/chat/completions requests.
This caused Gemini to return functionCalls instead of text, and since
the completions handler has no function call handling logic, it would
poll forever waiting for text that never came.
Fix: clear active_tools, active_tool_config, and has_active_function_call
at the start of handle_completions. Also add clear_active_function_call()
method to MitmStore.
When the MITM can't extract a cascade ID from the intercepted request
(Content-Length: 0 / chunked encoding), usage is stored under '_latest'.
Now usage_from_poll and completions try the exact cascade_id first,
then fall back to '_latest' so MITM-captured tokens are actually used.
