feat(core): keep scrap cutoffs clear of clamp zones

OpenNest.Core/AutomaticCutOffPlanner.cs

@@ -29,6 +29,7 @@ public enum AutomaticCutOffDiagnosticCode
     LimitedCutOffConflict,
     EmptyCut,
     SegmentedCut,
+    ClampBlockedCut,
     NoSafeTailSeparator,
     TailBelowMinimum,
 }
@@ -172,6 +173,22 @@ public static class AutomaticCutOffPlanner
 
         void AddCandidate(double x, bool isSeparator)
         {
+            // A full-width cut crosses every active front-edge clamp at this X. Test
+            // even equivalent existing definitions: a stale manual line cannot certify
+            // a retained tail. Keep the whole footprint when it hangs off the sheet.
+            var clearance = plate.EdgeSpacing.Bottom;
+            var blocked = plate.ClampZones.FirstOrDefault(zone =>
+                x >= zone.Bounds.Left - clearance && x <= zone.Bounds.Right + clearance);
+            if (blocked != null)
+            {
+                diagnostics.Add(new AutomaticCutOffDiagnostic(
+                    AutomaticCutOffDiagnosticCode.ClampBlockedCut,
+                    $"The proposed cut crosses clamp '{blocked.Id}' (including bottom-edge clearance); it was skipped.",
+                    X: x));
+                if (isSeparator)
+                    WarnNoSeparator(x);
+                return;
+            }
             var matches = plate.CutOffs.Where(c => c.Axis == CutOffAxis.Vertical &&
                 Near(c.Position.X, x)).ToList();
             if (matches.Any(c => !FullSpanLimits(c, bounds, settings)))
@@ -242,6 +259,11 @@ public static class AutomaticCutOffPlanner
             "Sheet length and width must be positive and finite.", nameof(plate));
         Require(plate.Quadrant is >= 1 and <= 4, "Quadrant must be 1 through 4.", nameof(plate));
         Require(Nonnegative(plate.PartSpacing), "Part spacing must be finite and nonnegative.", nameof(plate));
+        Require(plate.ClampZones != null && (plate.ClampZones.Count == 0 ||
+            Nonnegative(plate.EdgeSpacing.Bottom) && plate.ClampZones.All(zone =>
+                zone?.Bounds != null && ValidBox(zone.Bounds) &&
+                zone.Bounds.Length > 0 && zone.Bounds.Width > 0)),
+            "Clamp zones and bottom-edge clearance must be finite and valid.", nameof(plate));
         Require(Nonnegative(settings.PartClearance) && Nonnegative(settings.MinSegmentLength) &&
             Nonnegative(settings.Overtravel), "Cut-off settings must be finite and nonnegative.", nameof(settings));
         Require(Enum.IsDefined(settings.CutDirection), "Unknown cut direction.", nameof(settings));

OpenNest.Tests/CutOffs/AutomaticCutOffPlannerTests.cs

@@ -189,6 +189,61 @@ public class AutomaticCutOffPlannerTests
         Assert.Equal(80.5 + Tolerance.Epsilon, plan.UsedSpan);
     }
 
+    [Theory]
+    [InlineData(1)]
+    [InlineData(2)]
+    [InlineData(3)]
+    [InlineData(4)]
+    public void ClampWall_SkipsNominalLineAndRefusesTailSeparator(int quadrant)
+    {
+        var plate = MakePlate(quadrant);
+        var sign = quadrant is 2 or 3 ? -1 : 1;
+        plate.EdgeSpacing = new Spacing(0.25, 0.25);
+        plate.ClampZones.Add(new ClampZone("nominal", new Box(sign > 0 ? 35.1 : -35.3,
+            quadrant is 3 or 4 ? -0.625 : 0, 0.2, 0.625)));
+        plate.ClampZones.Add(new ClampZone("tail", new Box(sign > 0 ? 80.6 : -80.8,
+            quadrant is 3 or 4 ? -0.625 : 0, 0.2, 0.625)));
+        var before = plate.Parts.ToArray();
+        var plan = Plan(plate);
+        Assert.Equal(new[] { sign * 70.0 }, Positions(plan));
+        Assert.False(plan.HasSeparatedTail);
+        Assert.Equal(0, plan.TailLength);
+        Assert.Contains(plan.Diagnostics, d => d.Code == AutomaticCutOffDiagnosticCode.NoSafeTailSeparator);
+        Assert.Equal(before, plate.Parts.ToArray());
+        Assert.Empty(plate.CutOffs);
+    }
+
+    [Fact]
+    public void ClampOnlyBlocksItsInflatedSpan_AndRemovedClampStopsBlocking()
+    {
+        var plate = MakePlate();
+        plate.EdgeSpacing = new Spacing(0.25, 0.25);
+        plate.ClampZones.Add(new ClampZone("front", new Box(35.25, 0, 1.5, 0.625)));
+        var blocked = Plan(plate);
+        Assert.Equal(new[] { 70, 80.5 + Tolerance.Epsilon }, Positions(blocked));
+        Assert.True(blocked.HasSeparatedTail);
+        plate.ClampZones.Clear();
+        Assert.Equal(new[] { 35, 70, 80.5 + Tolerance.Epsilon }, Positions(Plan(plate)));
+    }
+
+    [Fact]
+    public void ExistingLineAcrossClampCannotCertifyTail_AndPartialFootprintBlocks()
+    {
+        var plate = MakePlate();
+        plate.EdgeSpacing = new Spacing(0.25, 0.25);
+        plate.ClampZones.Add(new ClampZone("hanging", new Box(80.6, 0, 0.2, 0.625)));
+        var existing = new CutOff(new Vector(80.5 + Tolerance.Epsilon, 0), CutOffAxis.Vertical);
+        plate.CutOffs.Add(existing);
+        existing.Regenerate(plate, new CutOffSettings());
+        var original = existing.Drawing.Program;
+        var plan = Plan(plate);
+        Assert.False(plan.HasSeparatedTail);
+        Assert.Null(plan.TailSeparatorX);
+        Assert.Contains(plan.Diagnostics, d => d.Code == AutomaticCutOffDiagnosticCode.NoSafeTailSeparator);
+        Assert.Same(original, existing.Drawing.Program);
+        Assert.Same(existing, Assert.Single(plate.CutOffs));
+    }
+
     [Fact]
     public void Planning_DoesNotMutateAnyLiveObjectsOrSequence()
     {

docs/automatic-scrap-cutoffs.md

@@ -21,7 +21,7 @@ Only real parts contribute to the occupied envelope; existing cutoff parts do no
 
 Cutoff trimming measures clearance from the part contour, excluding tagged lead-in and lead-out moves when building the closed outline. Leads must not turn a recessed outline into a convex hull and leave oversized gaps elsewhere. Genuinely open contours still use the conservative hull/bounds fallback. The conservative curve/offset approximation can leave a small extra gap (about 0.0003 in on a straight edge at the default 0.02-in clearance), not an extra quarter inch.
 
-If no safe separator fits inside the sheet, there is no retained-tail claim and the nominal cuts may cover the full sheet length. A proposed tail is not reported as separated unless its generated program spans the full sheet width. Obstructed or minimum-length-filtered lines produce diagnostics; they are not proof of a completed partition.
+If no safe separator fits inside the sheet, there is no retained-tail claim and the nominal cuts may cover the full sheet length. A proposed tail is not reported as separated unless its generated program spans the full sheet width. An active clamp blocks any proposed full-width line whose X coordinate falls in the clamp's whole footprint plus bottom-edge clearance, including a nominal grid line or an equivalent existing line. Blocked lines are skipped with a clamp diagnostic; a blocked tail also reports `NoSafeTailSeparator` rather than claiming separation. Removed clamps on a sheet are absent from its active zones and do not block cuts. Obstructed or minimum-length-filtered lines produce diagnostics; they are not proof of a completed partition.
 
 For a 120-by-81-inch sheet whose parts extend through 80 inches, the nominal skeleton lines are at 35 and 70 inches, followed by a separator beyond 80 inches at the required margin. There is no line at 105 inches through the retained tail.