fix(claude): deduplicate duplicate tool outputs in OpenAI-to-Claude request conversion

- Precompute the last tool message/output per `tool_call_id` in chat-completions and responses requests, then emit only one `tool_result` per call ID at its first position.
- Use the final payload for each duplicate tool call/output and preserve attachment of cache-control metadata from the final tool item.

Closes: #4997