Codex CLI compatibility:
- Skip non-function tool types (web_search, code_interpreter)
- Merge developer/system messages into position 0 for Qwen templates
- Strip Responses-only request keys (store, include, prompt_cache_key)
- output_text convenience field in streaming and non-streaming responses
Responses API compliance (ideas from #19720 by riskywindow, adapted):
- Add 24 missing Response object fields per OpenAI spec
- Fix function_call id/call_id field mapping
- Add sequence_number, output_index, content_index to streaming events
- Accept input_text type and EasyInputMessage for multi-turn input
Verified: codex -p local and codex -p fast work against local
llama.cpp with Qwen3.5 models including native tool calling.
Refs: ggml-org/llama.cpp#19138, ggml-org/llama.cpp#19720
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