The WorkHandler a host gives ConsumerRuntime. For each delivery it resolves a fresh BaseWorkHandler, mints a
provider, binds the execution context and delegates. The host checks the key resolves before starting a runtime;
the dead-letter branch covers a registration removed while the host runs. A provider-source failure propagates,
which ConsumerRuntime treats as Retry (03 §3.2).
The WorkHandler a host gives ConsumerRuntime. For each delivery it resolves a fresh BaseWorkHandler, mints a provider, binds the execution context and delegates. The host checks the key resolves before starting a runtime; the dead-letter branch covers a registration removed while the host runs. A provider-source failure propagates, which ConsumerRuntime treats as Retry (03 §3.2).