refactor: migrate example to new workflow API (#1467)

.changeset/warm-candles-explain.md

.changeset/weak-ducks-visit.md

examples/workflow/app-creator.ts

examples/workflow/conditional.ts

examples/workflow/joke.ts

examples/workflow/stream-events.ts

examples/workflow/timeout.ts

examples/workflow/validation.ts

packages/core/src/workflow/workflow.ts

packages/workflow/src/workflow-context.ts

packages/workflow/src/workflow.ts

pnpm-lock.yaml