Migrate core to the vanity module path

docs/internal/overview.md

@@ -6,6 +6,10 @@ own the optional ConfigKit and PromptKit integrations. The
 [architecture policy](../policy/architecture.md) owns normative boundaries;
 this page inventories the implemented owners.
 
+The core module now declares `go.maximumdirect.net/commandkit`. The integration
+modules retain their old module and core import identities until their planned
+matched releases; Go treats those identities as distinct.
+
 ## Root `commandkit`
 
 The root facade owns captured canonical command declarations, application-owned