Persist circuit group moves

docs/spec/09-distribution-board-components-and-protection-groups.md

@@ -663,8 +663,8 @@ Acceptance:
 ### D. Group Numbering and Circuit Moves
 
 Status: In progress. Group renumbering D1 and deterministic circuit-move
-planning D2a are complete; persistent moves D2b and populated deletion D3
-remain pending.
+planning and persistent moves D2 are complete; populated deletion D3 remains
+pending.
 
 - implement nested identifier generation
 - support same-category cross-group circuit moves
@@ -700,6 +700,17 @@ Implemented in D2a:
   and never fills gaps
 - the computed target BMK is part of the plan and is not recalculated for Redo
 
+Implemented in D2b:
+
+- `circuit.move-group` atomically changes only the circuit's group, BMK and
+  sort position
+- the circuit UUID remains stable, so its device rows and one-to-one protection
+  device remain connected without copying
+- execution revalidates project/list ownership, both group identities and the
+  complete expected circuit state
+- Undo/Redo uses the stored inverse move and late failures restore source
+  group, BMK and position
+
 Acceptance:
 
 - target identifiers use highest suffix plus one