From a diagram to a running workflow

Goal: end this skill with a workflow whose structure a reader can check line by line against the picture that produced it, registered and started once against Catalyst.

The picture is the specification. Everything here exists to keep it that way, because the failure that matters is not code that will not compile — you find that in seconds — it is code that compiles, runs, and quietly does something the diagram does not say.

1. Never go from the picture straight to code

Four phases, in this order, and the third does not begin until the second passes.