docs: snapshot Local G2 detector report order

docs/superpowers/plans/2026-07-30-local-g2-path-presmoothing.md

@@ -1194,14 +1194,26 @@ git commit -m "feat: validate local G2 candidate quality"
 - Create: `ClumsyPilot/tests/verify_path_smoothing_local_g2_integration.ps1`
 - Modify: `ClumsyPilot/tests/verify_path_smoothing_service.ps1`
 
+**Planned imports:**
+
+```csharp
+using System.Collections.ObjectModel;
+```
+
 **Interfaces:**
 
 - Consumes: validated request, prepared path and fair raw baseline.
-- Consumes `LocalG2RegionWorkOrder.TryCreate(...)`; pipeline iteration must not use report-order regions directly.
-- Publishes region reports in the detector's original ascending order, independently of processing order.
+- Snapshots detector-order regions into an immutable read-only `reportOrder` before
+  calling `LocalG2RegionWorkOrder.TryCreate(...)`; work-order creation does not
+  mutate this snapshot, and pipeline iteration must not use report-order regions
+  directly.
+- Publishes region reports by indexed iteration over `reportOrder` in the
+  detector's original ascending order, independently of processing order.
 - Produces:
 
 ```csharp
+private readonly LocalG2RegionWorkOrder _workOrder = new LocalG2RegionWorkOrder();
+
 internal PathSmoothingResult Smooth(
     PathSmoothingRequest request,
     PreparedPath preparedPath,
@@ -1291,8 +1303,11 @@ Expected: fail because the service cannot resolve `LocalG2Quintic`.
 Pipeline pseudocode must be implemented directly:
 
 ```csharp
+IReadOnlyList<LocalG2SmoothingRegion> reportOrder =
+    new ReadOnlyCollection<LocalG2SmoothingRegion>(new List<LocalG2SmoothingRegion>(regions));
+
 if (!_workOrder.TryCreate(
-        regions,
+        reportOrder,
         out IReadOnlyList<LocalG2SmoothingRegion> workRegions,
         out string orderReason))
 {
@@ -1350,9 +1365,9 @@ foreach (LocalG2SmoothingRegion region in workRegions)
     }
 }
 
-var reports = new List<PathSmoothingRegionReport>(regions.Count);
-for (int reportIndex = 0; reportIndex < regions.Count; reportIndex++)
-    reports.Add(reportsByRegion[regions[reportIndex]]);
+var reports = new List<PathSmoothingRegionReport>(reportOrder.Count);
+for (int reportIndex = 0; reportIndex < reportOrder.Count; reportIndex++)
+    reports.Add(reportsByRegion[reportOrder[reportIndex]]);
 ```
 
 Regions are disjoint after merging, so successful earlier replacements remain when a later region fails.