Port the cache usage mapping from #241 to current response converters and preserve zero and unavailable counts. Co-authored-by: Zeaxion <26239880+ChainZeaxion@users.noreply.github.com> Co-authored-by: OpenAI Codex <noreply@openai.com> Signed-off-by: yangzhuxinyzx <153831768+yangzhuxinyzx@users.noreply.github.com>