fix(agent): recover Responses streams with null output

[clarkchen]

Summary

Recover Codex/OpenAI Responses streams when the terminal response.output is null/None even though earlier stream events already delivered output items or text deltas.

This is the same failure mode described in #11179 and the same direction as #11182, adapted to this fork's current runtime split where the main Codex Responses stream lives in agent/codex_runtime.py rather than directly in run_agent.py.

Root Cause

Some Responses backends can emit valid response.output_item.done or response.output_text.delta events, then finish with a terminal response whose output field is null. The OpenAI SDK may raise TypeError: 'NoneType' object is not iterable while processing that terminal event, before Hermes can read the final response normally.

Changes

• Add shared Responses output backfill helpers in agent/codex_runtime.py.
• Recover the main Codex Responses stream path from SDK NoneType iteration crashes using collected output items or text deltas.
• Treat terminal output=None the same as empty output in the create(stream=True) fallback.
• Apply the same recovery to the auxiliary Responses adapter used by compression, memory, and related side-LLM flows.
• Add regression coverage for SDK TypeError recovery and direct output=None terminal responses.

Validation

• uv run --with pytest --with pytest-timeout --with pytest-asyncio python -m pytest tests/run_agent/test_run_agent_codex_responses.py tests/agent/test_auxiliary_client.py
• Result: 245 passed in 65.41s

[alt-glitch]

Duplicate of #32884. Same Codex null output recovery. Explicitly references #11179 and #11182 as prior art.

[clarkchen]

Duplicate of #32884. Same Codex null output recovery. Explicitly references #11179 and #11182 as prior art.

@alt-glitch Thanks — confirmed, this duplicates #32884. Closing this PR in favor of that one.