Add three state management components:
- LatencyBlockStateManager: tracks providers blocked due to
high latency with configurable block duration and scope
- LatencyTriggerCounter: counts consecutive latency threshold
breaches before triggering provider blocking
- RetryAfterStateManager: honors Retry-After headers with
per-provider/model/endpoint blocking scope
Signed-off-by: Troy Mitchell <i@troy-y.org>
