promote_scalars_to_edges

Apply `UPG_SCALAR_TO_EDGE_MIGRATIONS` graph-wide (P14 conformance): promote scalar properties that name a first-class entity into canonical edges. Per rule: find-or-create the referenced entity by normalized title, link it with the canonical edge, then drop the now-redundant scalar (unless the rule keeps it as an actor display-cache). Lossless (the string becomes a real node) and idempotent (re-running mints/links nothing new). Snapshot the .upg first. Default `dry_run=true` previews the per-rule plan (minted / linked / dropped / skipped); pass `dry_run=false` to commit. The rules are listed by `list_scalar_to_edge_migrations`.