* fix(logging): pass provider response headers to callbacks on every endpoint
Custom callbacks only received kwargs["response_headers"] for chat
completions. Responses, image generation and edit, speech, and
transcription calls either never recorded the provider's headers or
recorded them in one place and not the other.
Every handler now records the provider's httpx headers on the response's
hidden params as "headers" (raw) and "additional_headers" (processed,
with LiteLLM's own entries winning on a clash), and the logging object
derives model_call_details["response_headers"] from those hidden params
before cost calculation on the non-stream and both streaming success
paths, keeping a handler-set value authoritative. Binary speech responses
expose their hidden params to the standard logging payload, and the sync
OpenAI transcription request always fetches the raw response.
* test(images): point the legacy image and speech fakes at the raw response surface
Image generation now goes through the SDK's raw response so the provider headers can be read, and the speech binary response now carries hidden params. The unit fakes in the image generation, xinference, proxy provider, image edit, Vertex speech, and otel suites still pinned the old call surface and the old "no hidden params" assertion, so they read an uncalled mock or a fake response without headers.
* test(images): drop the rewritten mock comments and the generated edit PNGs
* test(images): move the llm-span test's image fake to the raw response surface
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Co-authored-by: mateo-berri <277851410+mateo-berri@users.noreply.github.com>
