SDK 0.4.28: resilient image build polling
Build-status polling now retries transient read timeouts, disconnects, and HTTP errors in sync and async clients. Retries use jittered backoff within the original build deadline and never resubmit the build. This prevents one transient shared poll failure from immediately failing all waiting rollouts.
Upgrade the SDK in the workload runner to receive this fix. No Verifiers API changes are required.
Validation: 76 focused client, Inspect, and polling tests pass, including eight waiters sharing a build through transient failures. Wheel and source distribution build successfully. The full 144-test suite has one local 512-upstream keepalive readiness failure, also reproduced against the unmodified client.