Plan circuit group renumbering

docs/spec/08-current-product-backlog.md

@@ -25,7 +25,10 @@ requirements and intended sequencing, not proof of implementation.
 - [x] Phase C2a2: component update and reorder commands.
 - [x] Phase C2b1: empty-group insert/update/delete commands.
 - [x] Phase C2b2: complete group reorder command.
-- [ ] Phase D: group numbering, moves and destructive operations.
+- [x] Phase D1a: deterministic collision-aware group-renumber plan.
+- [ ] Phase D1b: persistent collision-safe group-renumber command.
+- [ ] Phase D2: same-category cross-group circuit moves.
+- [ ] Phase D3: confirmed populated-group deletion.
 - [ ] Phase E: editor projection and editing.
 - [ ] Phase F: documentation and full GUI verification.
 - [ ] Keep full electrical sizing and cable-dimensioning rules separate until

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

@@ -662,11 +662,24 @@ Acceptance:
 
 ### D. Group Numbering and Circuit Moves
 
+Status: In progress. The deterministic renumber planner D1a is complete;
+persistent execution D1b, cross-group moves D2 and populated deletion D3
+remain pending.
+
 - implement nested identifier generation
 - support same-category cross-group circuit moves
 - implement explicit collision-safe group renumbering
 - implement confirmed populated-group deletion
 
+Implemented in D1a:
+
+- a pure renumber planner derives group prefixes, circuit BMKs and optional
+  upstream-protection/RCD BMKs from category and target group number
+- outgoing-circuit suffixes remain unchanged
+- number swaps are allowed only when every conflicting group participates
+- collisions with unchanged groups, no-op mappings and mismatched current BMKs
+  are rejected before persistence
+
 Acceptance:
 
 - target identifiers use highest suffix plus one