feat: add Codex tool example

[dkundel-openai]

Summary

• add a codex-tool.ts example that runs a Codex task through the agents SDK and surfaces the traced output
• expose the example via the tools workspace README and scripts so it can be launched with pnpm
• refresh the agents-extensions metadata to record the Codex SDK dependency

Testing

• pnpm -F tools build-check (fails: TypeScript cannot resolve @openai/agents until the workspace packages are built)
• pnpm build (fails: workspace packages need generated shims before the TypeScript compile succeeds in this environment)

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https://chatgpt.com/codex/tasks/task_i_69051690fb78833187722794386d7445

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