Write a working record's changes and set statusField to status. Columns a stage set directly
(Pipeline.columns) are always written; Pipeline.completionColumns only when the stage succeeded.
Commit a record another one produced (a discovered item, an archive member, a chunk). Re-runs produce the same records again, so a child is matched to its existing row by URL; an unchanged existing child is a no-op, and a changed one resets every downstream stage.
Writes the well-known fields that changed, plus the stage's status, through the standard save path. A commit is safe to repeat: nothing here depends on the record's prior state.