[Harness] Escalate to the user after N unproductive iterations #4092

Summary

When an agent is stuck on something only the user can unblock (missing connection, ambiguous request, required confirmation), it does not escalate to the user after a few unproductive iterations — it keeps looping silently instead of asking.

Simulated example

goal: act on an external service that isn't connected
→ try_service()  → not connected
→ try_service()  → not connected
(never says: "Service X isn't connected — connect it in Settings, or tell me how to proceed")

Expected behavior

After N unproductive iterations (or on a clearly user-actionable blocker), pause and ask the user a specific question or give a clear next step, instead of continuing to loop.

Suggested fix / acceptance

• Detect user-actionable blockers (missing connection/permission, ambiguity) and prompt immediately.
• Otherwise escalate to the user after N idle iterations with a concise status + concrete ask.

Surfaced by our internal agent-simulation harness during large-scale, aggressive fuzz testing of agent behaviors. The example above is synthetic and contains no real data.