There's a Review Skill Already Bundled

You ask a reviewer for gaps, and it finds some, whether or not any exist. That's the part people miss before they build their own review workflow: /code-review already ships with the tool. It runs in a subagent, a separate process with no memory of writing the code, so it reviews the diff instead of defending it.

That covers most of what people build the writer/reviewer pattern for, at zero setup.

One thing to add to its brief, and it applies to every reviewer you ever configure: scope it to correctness. Left unscoped, it will flag real gaps and invented ones alike, and fixing all of them is how a simple feature quietly acquires extra abstraction layers it didn't need.