Replacement migrations must close legacy creation paths

When a workflow is replaced, keep pinned historical records resolvable while removing, archiving, or explicitly gating the superseded option on every new-creation surface. Referential stability for old records does not require continued discoverability for new records.

This applies when records pin immutable configuration identifiers. If historical records resolve configuration dynamically, first define a separate compatibility and migration strategy. Validate both halves: intended new inputs reach the replacement, and new work cannot enter the legacy path except through an intentional compatibility override.