setup-upstream-fix

This skill turns a Magpie skill or tool that misbehaved during a run into a fix PR in apache/magpie. Its sibling setup-override-upstream promotes a deliberate local override; this one fixes an unintended defect — a broken helper, a path left stale by a rename, a field read at the wrong nesting, a confusing hard-failure — so every later adopter gets the repair.