Implement a conditional branch and a self-referential recursive step in a Metaflow flow (2.18+)

Steps

1. In a step, compute a value and call `self.next({key1: self.stepA, key2: self.stepB}, condition='<artifact_name>')` to pick exactly one branch
2. Ensure every possible value of the condition artifact has a corresponding dictionary key mapped to a step
3. For recursion, define a step whose `self.next(...)` dict includes itself as one of the branch targets, guarded by a condition artifact
4. Track loop state in an instance variable (e.g. increment a counter each pass) so the condition can eventually route to termination
5. If the flow fails mid-recursion, use `python myflow.py resume` to continue from the last successful iteration