fix #844: add resume helpers for MaxTurnsExceeded runs

[thomas-lab-openai]

This pull request resolves #844:

• add async resume() and sync resume_sync() helpers on MaxTurnsExceeded that replay one final turn with an optional user prompt, reusing the prior agent, context, and a copy of the original RunConfig
• extend RunResult and RunErrorDetails to retain the effective RunConfig, so guardrail/tool settings, tracing metadata, and other knobs survive into a resume attempt
• ensure resume turns disable further tool calls by forcing tool_choice="none" while still respecting any other model settings (e.g., temperature) that the caller supplied
• cover the new helpers with unit tests for async/sync flows, verify model-settings preservation, and document the flow via a examples/basic/max_turns_resume.py sample that demonstrates recovering after a hard turn limit