Split equivalent policy updates when live writers invert locks

A migration that locks several active tables can deadlock with writers whose transactions acquire those relations in a different order. Increasing acquisition timeouts does not remove the inversion. When every replacement policy independently preserves the same access semantics, create its helper definitions first, then update each policy in its own transaction. This reduces simultaneous lock ownership without an interval of missing enforcement. Do not split changes that require coordinated state or whose mixed states admit access; establish equivalence before choosing this delivery method. Applies when: Live writers prevent a multi-table authorization migration from completing. Keywords: migration deadlock lock inversion policy update transaction live writer