Manage circuit groups

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

@@ -741,7 +741,8 @@ Acceptance:
 
 Status: In progress. The complete tree read model E1, pure structural
 projection E2a, grid rendering E2b and mutable component editing E3a are
-complete. Group management and circuit-protection editing remain pending.
+complete. Basic group management E3b1 is also complete. Circuit-protection
+editing and structural drag/renumber/delete workflows remain pending.
 
 - render fixed header components
 - render group components and circuit blocks
@@ -770,6 +771,12 @@ Implemented in E1/E2a/E2b/E3a:
 - mutable group protection and auxiliary footer components use labeled modals,
   type-dependent protection fields and persistent project commands
 - fixed main-switch and surge-protection header components remain read-only
+- users can create a group in any supported category; its number is the
+  category's highest existing number plus one and its prefix is generated
+- group editing changes only the display name; category, number, prefix and
+  child BMKs remain stable
+- an exactly empty group can be removed through the persistent group command;
+  populated deletion stays disabled until the dedicated warning UI is present
 
 Acceptance: