When Bedrock rejects a request with "data retention mode '<mode>' is not
available for this model", append a pointer to the AWS data retention
documentation so users can configure a supported mode.
Azure Foundry deploys gpt-5.4 and gpt-5.5 with a 1,050,000 context
window, but the Azure provider cloned OpenAI-direct's 272k API limit.
Override the context window in the Azure derivation.
Also fix gpt-5-pro maxTokens, which upstream metadata set to 272000 (a
duplicate of the input sub-limit) instead of the actual 128000 max
output; corrected at the source so OpenAI-direct and Azure both match.
closes#5559
Application inference profile ARNs encode the region
(arn:aws:bedrock:<region>:<account>:...) but the provider ignored it,
falling through to AWS_REGION which may point to a different region.
Extract the region from the ARN when present, taking priority over
environment variables.
Fixes#4860