feat: add p-rec-annot Plant line-number candidate reader

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

@@ -63,6 +63,7 @@ public sealed record LineNumberApplyPreflight(string StableId, int MarkerNumber,
 public sealed record LineNumberApplyResult(int Created, int Updated, int Unchanged);
 public sealed record LineNumberListApplyPreflight(string StableId, AnnotationPoint Position, double Rotation, IReadOnlyList<LineNumberApplyPreflight> Rows);
 public sealed record LineNumberPreviewResult(bool Success, LineNumberCommandPlan? Plan, IReadOnlyList<LineNumberApplyPreflight> Apply, string? FailureCode = null);
+public sealed record LineNumberCandidateReadResult(bool Success, LineNumberCandidate? Candidate, string? FailureCode = null);
 public sealed record LineNumberTextAsset(string Layer, string TextStyle, double Size, string TextValue, Point2Dto Position);
 public sealed record LineNumberLineAsset(string Layer, Point2Dto Start, Point2Dto End);
 public sealed record LineNumberMarkerAsset(string Layer, double MaskScaleFactor, IReadOnlyList<LineNumberTextAsset> Texts, IReadOnlyList<LineNumberLineAsset> Lines);

Plant3D2026/P_Rec_Annot/src/PRecAnnot.Plant3D2026/PlantLineNumberCandidateReader.cs

@@ -0,0 +1,36 @@
+using Autodesk.AutoCAD.DatabaseServices;
+using Autodesk.AutoCAD.Geometry;
+using Autodesk.ProcessPower.DataLinks;
+using PRecAnnot.Abstractions;
+
+namespace PRecAnnot.Plant3D2026;
+
+// Converts an explicit AutoCAD selection to the small, AutoCAD-free candidate
+// used by the line-number preview.  It deliberately performs no DataLinks or
+// DWG write and reports unavailable Plant mappings as typed failures.
+internal sealed class PlantLineNumberCandidateReader(DataLinksManager dataLinks)
+{
+    public LineNumberCandidateReadResult Read(ObjectId selectedId, string layer, string textStyle)
+    {
+        if (selectedId.IsNull || !selectedId.IsValid) return new(false, null, "LINE_NUMBER_SELECTION_INVALID");
+        if (string.IsNullOrWhiteSpace(layer) || string.IsNullOrWhiteSpace(textStyle)) return new(false, null, "LINE_NUMBER_ASSET_CONTRACT_INVALID");
+        try
+        {
+            var rowId = dataLinks.FindAcPpRowId(selectedId);
+            if (rowId <= 0) return new(false, null, "LINE_NUMBER_DATALINKS_ROW_NOT_FOUND");
+            var database = selectedId.Database;
+            using var transaction = database.TransactionManager.StartOpenCloseTransaction();
+            if (transaction.GetObject(selectedId, OpenMode.ForRead) is not Entity entity) return new(false, null, "LINE_NUMBER_SELECTION_NOT_ENTITY");
+            var extents = entity.GeometricExtents;
+            var center = new Point3d(
+                (extents.MinPoint.X + extents.MaxPoint.X) / 2d,
+                (extents.MinPoint.Y + extents.MaxPoint.Y) / 2d,
+                (extents.MinPoint.Z + extents.MaxPoint.Z) / 2d);
+            transaction.Commit();
+            return new(true, new($"acad:{selectedId.Handle}", rowId, new(center.X, center.Y, center.Z), 0, layer, textStyle, new Dictionary<string, string?>()));
+        }
+        catch (Autodesk.AutoCAD.Runtime.Exception) { return new(false, null, "LINE_NUMBER_SELECTION_GEOMETRY_UNAVAILABLE"); }
+        catch (DLException) { return new(false, null, "LINE_NUMBER_DATALINKS_ROW_NOT_FOUND"); }
+        catch (Exception) { return new(false, null, "LINE_NUMBER_CANDIDATE_READ_FAILED"); }
+    }
+}