feat: implement first limited Pipe annotation Apply

Plant3D2026/P_Rec_Annot/src/PRecAnnot.Abstractions/Contracts.cs

@@ -177,6 +177,10 @@ public sealed record AnnotationPlanningRequest
     public required OrthoViewportInfo Viewport { get; init; }
     public IReadOnlyList<PlantObjectSnapshot> Objects { get; init; } = Array.Empty<PlantObjectSnapshot>();
     public IReadOnlyList<ExistingAnnotation> Existing { get; init; } = Array.Empty<ExistingAnnotation>();
+    // Test-only limited Apply intent.  It is part of the canonical plan and is
+    // deliberately explicit: the planner must never choose an arbitrary Pipe.
+    public string? LimitedApplyTargetSnapshotId { get; init; }
+    public string? LimitedApplyRuleId { get; init; }
 }
 
 public interface IAnnotationPlanBuilder { AnnotationPlan Build(AnnotationPlanningRequest request); }