Add circuit group commands

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

@@ -593,8 +593,9 @@ Acceptance:
 
 ### C. Persistent Commands and Board Defaults
 
-Status: In progress. New-board defaults C1 and component management C2a are
-complete. Group management C2b remains pending.
+Status: In progress. New-board defaults C1, component management C2a and
+empty-group CRUD C2b1 are complete. Complete group reordering C2b2 remains
+pending.
 
 - extend `distribution-board.insert` with fixed components and three groups
 - implement component and group CRUD commands
@@ -635,6 +636,17 @@ Implemented in C2a2:
 - stale expected state and cross-entity BMK collisions are rejected; Undo/Redo
   restores the exact previous snapshot
 
+Implemented in C2b1:
+
+- `circuit-group.insert`, `circuit-group.update` and
+  `circuit-group.delete` persist complete group snapshots with stable UUIDs
+- category, group number and prefix are validated as one consistent identity;
+  general updates change only the display name
+- deletion requires an exact unchanged and empty group; populated destructive
+  deletion remains the separately confirmed Phase-D operation
+- project/list ownership, stale state, Undo/Redo and late rollback are covered
+  at the shared transaction boundary
+
 Acceptance:
 
 - new boards contain the agreed fixed structure