Drop the new `artifacts=` keyword on `request_review()` and its
`_declare_handoff_artifacts` helper: the tool layer already folds the
model-facing `artifacts` list into `metadata["artifacts"]` via the
existing `_merge_artifacts`, so the DB layer needs only the one input it
already honours. Keep two invariant tests (declared artifact survives the
reviewer's completion; notifier uploads the staged copy on
`review_requested`); the prose-reference and rollback variants are
covered by the same helpers `complete_task` already exercises.
Salvage of #109276 by @yoyodine-industries.
d1cf019561