The /openai/responses endpoint forwarded the prefixed model id (e.g.
"myprovider.gpt-4o") to the upstream provider instead of the stripped
native name, causing "model not found" errors when a connection has a
Prefix ID configured.
generate_chat_completion() already strips the prefix before forwarding;
apply the same strip_provider_model_prefix() call in responses() after
the urlIdx routing (which needs the prefixed id) and re-serialize the
body afterwards.
Also fixes the Azure non-v1 deployment path, which built the deployment
URL from the prefixed model name.
Co-authored-by: Claude <noreply@anthropic.com>
