fix(loop): only mention the expanded retry in runaway guidance when it ran

[zhanghanduo]

Summary

Runaway recovery is a ladder: expanded thinking → reduced thinking → thinking off. The first phase is skipped when RUNAWAY_MAX_RETRIES < 3 (_RUNAWAY_EXPAND_ENABLED is false) or when the expanded cap cannot fit the context. In both cases the first retry goes straight to the reduced phase, but its reminder still said:

The expanded-thinking retry still produced no visible answer or tool call…

so the model was told about an attempt it never saw.

call_llm now records whether an expanded retry actually ran (runaway_expanded) and passes it to _runaway_retry_policy(..., expanded_attempted=...). The reduced phase uses the existing reminder after a real expanded retry (including the context-overflow path, where the expanded attempt did run), and a new _RUNAWAY_REDUCED_GUIDANCE otherwise, which carries the same instruction without referring to a phase that never ran. The keyword defaults to True, so other callers keep today's behaviour. Retry counts, caps and thinking overrides are unchanged.

Found while migrating FrontierAgent onto AgentCore (ApodexAI/FrontierAgent#50), where *_RUNAWAY_MAX_RETRIES=2 is the documented way to keep cap-only retries.

Test plan

• New tests/test_runaway_retry_guidance.py:
  • policy-level: the reduced reminder mentions the expanded retry only when expanded_attempted=True;
  • end-to-end through call_llm with expansion disabled: the retry request's reminder does not mention an expanded retry.
  • Both fail on main, pass with the fix.
• Release fragment changes/runaway-guidance-without-expansion.fix.md; check_version_bump.py passes
• ruff, pyright agent_core, full pytest -q (1603 passed)

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