ProviderRequest loses reasoning_summary, service_tier, output_format_name,
previous_response_id and prompt_cache_key; reasoning_effort is a ReasoningEffort,
max_output_tokens is required and cache_retention is added. Completed carries a
StopReason and Usage, Failed a FailureKind, and the receipt names its provider.
Refusal::Policy becomes ModelNotAllowed, OutputBound and PayloadBound, each its
own branch in begin. cultcache-rs moves to the one CultLib pin a4eae90.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>