Add proxy_failure_limit param to make_tiered_cycler (default 3).
Individual proxies hitting the limit are marked dead and permanently
skipped. next_proxy() auto-escalates when all proxies in the active
tier are dead. Both mechanisms coexist: per-proxy dead tracking removes
broken individuals; tier-level threshold catches systemic failure.
- proxy.py: dead_proxies set + proxy_failure_counts dict in state;
next_proxy skips dead proxies with bounded loop; record_failure/
record_success accept optional proxy_url; dead_proxy_count() added
- playtomic_tenants.py: pass proxy_url to record_success/record_failure
- playtomic_availability.py: _worker returns (proxy_url, result);
serial loops in extract + extract_recheck capture proxy_url
- test_supervisor.py: 11 new tests in TestTieredCyclerDeadProxyTracking
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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