synthesizeOpenAiSseFromJson combined role+content+reasoning_content in one delta, which the openai→openai translator re-split, duplicating reasoning_content across chunks. Now emits role, reasoning_content, content and tool_calls as separate sequential deltas (reasoning before content) — the shape a real reasoning model streams — so the translator passes them through with no duplication. Tests assert each field appears exactly once and reasoning precedes content.
#3089: reasoning openai-compatible upstreams that ignore stream:true and return application/json produced STREAM_EARLY_EOF because readiness only scans SSE data: frames. chatCore now detects a non-SSE JSON upstream body on the streaming path and synthesizes an equivalent OpenAI SSE stream (new synthesizeOpenAiSseFromJson util), preserving content + reasoning_content. #2952: semantic-cache hits returned application/json regardless of stream flag, so streaming clients lost reasoning_content; stream requests now SSE-wrap the cached completion via the same helper. Unit tests for the converter (4).
