A completion workflow on Temporal with signals and a deadline

All side effects and anything non-deterministic live in four activities on one Activities class. The workflow only orders them, holds the decision state and waits. The decision that matters most is where each piece of state lives: the lender's call count, the execution log and the outbox are files outside the worker, so killing and restarting the worker shows what Temporal replays and what it really re-executes. A second run under changed code shows what Temporal does when the code no longer matches a waiting run's history.