Shape.SetLine writes through the indexer so it invalidates the caches; footprint tests pin refusal Position and a wide shape

Builds: yes (Shared-only; verified on Yggdrasil in the report).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/ItemData.cs

@@ -276,7 +276,7 @@ public class Shape
         {
             if (x >= 0 && x < Width && y >= 0 && y < Height)
             {
-                Cells[steep ? y : x, steep ? x : y] = true;
+                this[int2(steep ? y : x, steep ? x : y)] = true;
             }
             error += derr;
             if (error >= 0.5f)

tests/Aetheria.Shared.Tests/HullFootprintTests.cs

@@ -72,6 +72,33 @@ public sealed class HullFootprintTests
         Assert.Equal(new[] { new int2(3, 3) }, Hull(hp));
     }
 
+    [Fact]
+    public void RefusedClickLeavesPositionWhereItWasWhenTheLastCellIsNotAtPosition()
+    {
+        var hp = Hardpoint(new int2(3, 3), new int2(1, 0));
+        Assert.Equal(new[] { new int2(4, 3) }, Hull(hp));
+
+        Assert.False(HullFootprint.Toggle(hp.Shape, hp.Position, new int2(4, 3), out var shape, out var position));
+
+        Assert.Equal(new int2(3, 3), position);
+        Assert.Same(hp.Shape, shape);
+    }
+
+    [Fact]
+    public void WideFootprintLaysEveryCellAtPositionAndEditsAtItsFarEnd()
+    {
+        var hp = Hardpoint(new int2(2, 2), new int2(0, 0), new int2(1, 0), new int2(2, 0), new int2(3, 0), new int2(4, 0));
+        Assert.Equal(new[] { new int2(2, 2), new int2(3, 2), new int2(4, 2), new int2(5, 2), new int2(6, 2) }, Hull(hp));
+
+        var grown = Apply(hp, new int2(7, 2));
+        Assert.Equal(new int2(2, 2), grown.Position);
+        Assert.Equal(new[] { new int2(2, 2), new int2(3, 2), new int2(4, 2), new int2(5, 2), new int2(6, 2), new int2(7, 2) }, Hull(grown));
+
+        var trimmed = Apply(hp, new int2(6, 2));
+        Assert.Equal(new int2(2, 2), trimmed.Position);
+        Assert.Equal(new[] { new int2(2, 2), new int2(3, 2), new int2(4, 2), new int2(5, 2) }, Hull(trimmed));
+    }
+
     [Fact]
     public void FootprintToggleLeavesItsInputUnchanged()
     {

tests/Aetheria.Shared.Tests/ShapeCacheTests.cs

@@ -50,4 +50,19 @@ public sealed class ShapeCacheTests
         Assert.False(shape[int2(1, 0)]);
         Assert.True(shape[int2(2, 0)]);
     }
+
+    [Fact]
+    public void SetLineRecountsEveryCoordinateRead()
+    {
+        var shape = new Shape(4, 1);
+        shape[int2(0, 0)] = true;
+        Assert.Single(shape.Coordinates);
+        Assert.Equal(0f, shape.CenterOfMass.x);
+
+        shape.SetLine(float2(0f, 0f), float2(3f, 0f));
+
+        Assert.Equal(4, shape.Coordinates.Length);
+        Assert.Equal(4, shape.AllCoordinates.Length);
+        Assert.Equal(1.5f, shape.CenterOfMass.x);
+    }
 }