fix: Support streaming of non-OpenAI models that return "ping"

[iBotPeaches]

What:

• Bug Fix

Description:

When running streaming from Claude in OpenAI compatibility mode we find that Claude returns a payload structure (shortened) like this.

data: {"id":"msg_0111RgCFCqN68mJbev6Rq1cz","choices":[{"index":0,"delta":{"role":"assistant"}}],"created":1744469024,"model":"claude-3-7-sonnet-20250219","object":"chat.completion.chunk"}
data: {"type": "ping"}
data: {"id":"msg_0111RgCFCqN68mJbev6Rq1cz","choices":[{"index":0,"delta":{"content":"Hello!"}}],"created":1744469024,"model":"claude-3-7-sonnet-20250219","object":"chat.completion.chunk"}
data: [DONE]

Related:

fixes: #555