setInitialStep
Set which step the context starts on when entered. By default, a context
starts on its first step (index 0). Use this to skip a preamble step on
re-entry via change_context.
The step name is validated by ContextBuilder.validate() — the target step
must exist in this context or validation throws.
Parameters
stepName
The step to start on when the context is entered. Must be an existing step in this context.
Returns
Context — self for method chaining.