Added criterion benchmarks and optimized flatten_tool_result_content:
- Added criterion dev-dependency and request_building benchmark suite
- Optimized flatten_tool_result_content to pre-allocate capacity and avoid
intermediate Vec construction (was collecting to Vec then joining)
- Made key functions public for benchmarking: translate_message,
build_chat_completion_request, flatten_tool_result_content,
is_reasoning_model, model_rejects_is_error_field
Benchmark results:
- flatten_tool_result_content/single_text: ~17ns
- translate_message/text_only: ~200ns
- build_chat_completion_request/10 messages: ~16.4µs
- is_reasoning_model detection: ~26-42ns
All 119 unit tests and 29 integration tests pass.
cargo clippy passes
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
