Sheet metal: sheet.perforate, a perforation field exported to the flat pattern and DXF (#732) (#1041)

Adds sheet.perforate: round holes on a staggered or square grid over the flat sheet, kept clear of edges, cut-outs and bend zones. The holes go to the flat pattern, the DXF and the measured volume rather than the B-rep, so a panel can carry many thousands of them.

crates/doc/src/document.rs

@@ -808,6 +808,20 @@ pub enum FeatureKind {
         #[serde(default, skip_serializing_if = "Option::is_none")]
         body: Option<String>,
     },
+    /// A perforation field (#732): round holes of `diameter` on a staggered (60°) or square grid of `pitch` over the
+    /// whole flat sheet, kept `margin` (default: the diameter) clear of its edges, cut-outs and bend zones. Stored like
+    /// a cosmetic thread: the holes go to the flat pattern, the DXF and the measured volume, not into the B-rep, so a
+    /// panel can carry tens of thousands of them.
+    SheetPerforate {
+        diameter: String,
+        pitch: String,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        margin: Option<String>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        pattern: Option<String>,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        body: Option<String>,
+    },
     /// Fold a sheet along a line on its base face: a sketch line (followed when the sketch
     /// changes), else the points `a`, `b`.
     SheetFold {
@@ -1354,6 +1368,7 @@ impl FeatureKind {
                 | FeatureKind::SheetContour { .. }
                 | FeatureKind::SheetFlange { .. }
                 | FeatureKind::SheetHem { .. }
+                | FeatureKind::SheetPerforate { .. }
                 | FeatureKind::SheetFold { .. }
                 | FeatureKind::SheetUnfold { .. }
                 | FeatureKind::SheetConvert { .. }
@@ -1407,6 +1422,7 @@ impl FeatureKind {
             FeatureKind::SheetContour { .. } => "ContourFlangeFeature",
             FeatureKind::SheetFlange { .. } => "EdgeFlangeFeature",
             FeatureKind::SheetHem { .. } => "HemFeature",
+            FeatureKind::SheetPerforate { .. } => "PerforateFeature",
             FeatureKind::SheetFold { .. } => "FoldFeature",
             FeatureKind::SheetUnfold { refold: false, .. } => "UnfoldFeature",
             FeatureKind::SheetUnfold { .. } => "RefoldFeature",
@@ -1480,6 +1496,7 @@ impl FeatureKind {
             FeatureKind::SheetContour { .. } => "ContourFlange",
             FeatureKind::SheetFlange { .. } => "EdgeFlange",
             FeatureKind::SheetHem { .. } => "Hem",
+            FeatureKind::SheetPerforate { .. } => "Perforate",
             FeatureKind::SheetFold { .. } => "Fold",
             FeatureKind::SheetUnfold { refold: false, .. } => "Unfold",
             FeatureKind::SheetUnfold { .. } => "Refold",