docs(plans): instance picker — node shape + orphan rules as shipped; task 1 complete

Claude-Session: https://claude.ai/code/session_01NcMG6xXdsJbmD2wYAgkK29

docs/plans/2026-09-08-instance-picker-design.md

@@ -46,7 +46,7 @@ Alternatives rejected:
 
 A parent that changes `Areas`/`Instances` (site change) resets the field text and closes the panel; a parent that changes `SelectedInstanceId` (URL / localStorage restore) updates the field text.
 
-**Pure builder.** `InstanceTreeBuilder.Build(areas, instances, filter)` → `IReadOnlyList<InstanceTreeNode>` (`Components/Shared/InstanceTreeNode.cs`, `InstanceTreeBuilder.cs`; record `InstanceTreeNode(string Key, string Label, Area? Area, Instance? Instance, List<InstanceTreeNode> Children)`, keys `a:{id}` / `i:{id}`, `IsInstance => Instance != null`). Orphaned areas (parent id pointing nowhere) are treated as roots so a bad row can never hide a subtree. `Topology.razor` keeps its own richer `TopoNode` — not refactored (YAGNI).
+**Pure builder.** `InstanceTreeBuilder.Build(areas, instances, filter)` → `IReadOnlyList<InstanceTreeNode>` (`Components/Shared/InstanceTreeNode.cs`, `InstanceTreeBuilder.cs`; record `InstanceTreeNode(string Key, string Label, Area? Area, Instance? Instance)` with a read-only `Children` property the builder fills, keys `a:{id}` / `i:{id}`, `IsInstance => Instance != null`). Orphaned areas (parent id pointing nowhere) and orphaned instances (area id pointing nowhere) are treated as roots so a bad row can never hide a subtree; a `ParentAreaId` cycle is unreachable from any root and simply does not render (guarded against looping). `Topology.razor` keeps its own richer `TopoNode` — not refactored (YAGNI).
 
 ## 3. Page wiring
 

docs/plans/2026-09-08-instance-picker.md.tasks.json

@@ -4,12 +4,12 @@
     {
       "id": 1,
       "subject": "Task 1: InstanceTreeNode + InstanceTreeBuilder (pure) with tests",
-      "status": "pending"
+      "status": "completed"
     },
     {
       "id": 2,
       "subject": "Task 2: InstancePicker component \u2014 field, panel, select, outside-click",
-      "status": "pending",
+      "status": "in_progress",
       "blockedBy": [
         1
       ]