Collect and return direct response traces - #183

Summary

• add AgentResponse.trace and best-effort parsing of direct response-trace records
• wire native and Pyodide Agent.run to response.trace without adapting legacy traces
• add runnable Operator and Agent Studio examples plus a combined notebook
• display the flat trace and parent/child hierarchy without introducing span-level billing fields
• preserve existing request-level AgentResponse.usage, action_trace, and workflow_trace behavior

Testing

• focused response-model, response-record, export, and Agent suites: 40 passed
• Ruff check and format passed for changed files

Codex sibling refs

• caddie: https://github.com/NaradaAI/caddie/pull/6887
• frontend: https://github.com/NaradaAI/frontend/pull/2062
• architecture-docs: https://github.com/NaradaAI/architecture-docs/pull/74
• desktop-automation-app:
• api-docs: