Add a mandatory final register-trim pass to multi-reviewer writing skills

In agent skills that run correctness and style reviewers over generated write-ups, add an explicit last phase that (1) compares structure against prior accepted artifacts from the same context and removes anything they never contain, (2) trims to the target register, and (3) re-briefs the checker to flag only cuts that are actually required. Without it, each review round adds defensible caveats and the result drifts toward over-polished output the user then asks to undo.