Decoder for OpenAI compatible chat.completion.chunk SSE streams — OpenAI, Groq, Mistral, DeepSeek, XAI, Zai, Cerebras, LiteLLM, Ollama, …

stream_event/1 converts a decoded chunk json map into a list of normalized stream events:

• {:text, binary} — content delta
• {:thinking, binary} — reasoning delta (reasoning_content / reasoning)
• {:tool_call, map} — tool call delta (raw provider shape)
• {:usage, map} — normalized usage, when the provider emits it (OpenAI requires stream_options: %{include_usage: true})
• {:finish, atom} — normalized stop reason