WHAT: Implement Responses API adapter with full SSE streaming support to enable Kode CLI working with GPT-5 and other models that require OpenAI Responses API format
WHY: GPT-5 and newer models use OpenAI Responses API (different from Chat Completions) which returns streaming SSE responses. Kode CLI needed a conversion layer to translate between Anthropic API format and OpenAI Responses API format for seamless model integration
HOW: Created ResponsesAPIAdapter that converts Anthropic UnifiedRequestParams to Responses API format (instructions, input array, max_output_tokens, stream=true), added SSE parser to collect streaming chunks and convert back to UnifiedResponse format. Fixed ModelAdapterFactory to properly select Responses API for GPT-5 models. Updated parseResponse to async across all adapters. Added production tests validating end-to-end conversion with actual API calls
