A session wedged against an unresponsive OpenAI-compatible provider can hit the stale-stream detector on every turn and loop forever, burning the full 180s x retries each turn with no response. Issue #58962 reports 494 consecutive failures over 3+ days on a single session.
The streaming retry path already caps retries WITHIN a turn (HERMES_STREAM_RETRIES, default 2) but has no cross-turn cap. Once a session's conversation state makes every turn stale, it retries indefinitely across turns and never notifies the user.
Add a per-session consecutive-stale-stream counter on the agent:
- incremented on every stale-stream kill in the outer poll loop;
- reset to 0 only when a stream actually completes;
- when it reaches HERMES_STREAM_STALE_GIVEUP (default 5), the next turn aborts immediately with a clear, actionable RuntimeError instead of spending 180s x retries again.
This is distinct from the existing stale-stream work (local-provider hard ceiling #44938, backoff/parse-error #60031): those bound a single hung stream, while this bounds repeated cross-turn staleness and surfaces a user-visible error.
Adds tests/run_agent/test_stream_stale_circuit_breaker.py covering the short-circuit, the success-reset, and the increment.
