- Introduced `claudeResponsesUsageTokens` to manage detailed token statistics, including input, output, cache read, and cache creation tokens.
- Updated aggregation logic to include cached tokens in total usage calculations.
- Refactored usage processing to simplify token merging and ensure consistent handling across streaming and non-streaming responses.
- Added unit tests (`TestConvertClaudeResponseToOpenAIResponses_ReportsCacheTokens`) to verify correct cache token inclusion in usage metrics.
Closes: #3807