Add component update commands

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

@@ -593,9 +593,8 @@ Acceptance:
 
 ### C. Persistent Commands and Board Defaults
 
-Status: In progress. New-board defaults C1 and component insert/delete commands
-C2a1 are complete. Component update/reorder and group management remain
-pending.
+Status: In progress. New-board defaults C1 and component management C2a are
+complete. Group management C2b remains pending.
 
 - extend `distribution-board.insert` with fixed components and three groups
 - implement component and group CRUD commands
@@ -626,6 +625,16 @@ Implemented in C2a1:
   component UUID and a late revision/history failure rolls back the complete
   write
 
+Implemented in C2a2:
+
+- `distribution-board-component.update` exchanges one complete expected
+  component/protection snapshot for one complete target snapshot
+- name, BMK, protection configuration and `sortOrder` can change atomically
+- component id, list/group ownership, role and placement zone remain immutable
+  through this general update command
+- stale expected state and cross-entity BMK collisions are rejected; Undo/Redo
+  restores the exact previous snapshot
+
 Acceptance:
 
 - new boards contain the agreed fixed structure