docs: add Rewind to external tracing processors list

Adds Rewind to the ecosystem integrations list in docs/tracing.md.
Rewind provides a TracingProcessor that captures agent spans into
a local time-travel debugger.

Closes openai#2872

Author: afurm

docs/tracing.md

@@ -207,6 +207,7 @@ The following community and vendor integrations support the OpenAI Agents SDK tr
 -   [AgentOps](https://docs.agentops.ai/v1/integrations/agentssdk)
 -   [Scorecard](https://docs.scorecard.io/docs/documentation/features/tracing#openai-agents-sdk-integration)
 -   [Respan](https://respan.ai/docs/integrations/tracing/openai-agents-sdk)
+-   [Rewind](https://github.com/agentoptics/rewind)
 -   [LangSmith](https://docs.smith.langchain.com/observability/how_to_guides/trace_with_openai_agents_sdk)
 -   [Maxim AI](https://www.getmaxim.ai/docs/observe/integrations/openai-agents-sdk)
 -   [Comet Opik](https://www.comet.com/docs/opik/tracing/integrations/openai_agents)