rework stroke width/miter not to conflict w poly internals

src/load/svg.js

@@ -41,8 +41,7 @@ function parse(text, opt = { soup: true }) {
                     let poly = base.newPolygon().addPoints(path.map(p => base.newPoint(p.x, -p.y, 0)));
                     if (poly.appearsClosed()) poly.points.pop();
                     if (type === 'polyline') poly.setOpen(true);
-                    if (width) poly.width = width;
-                    if (miter) poly.miter = miter;
+                    poly._svg = { width, miter };
                     polys.push(poly);
                 }
             }

src/mesh/sketch.js

@@ -429,10 +429,11 @@ mesh.sketch = class MeshSketch extends mesh.object {
         // log(this.file || this.id, '| add polygon');
         let poly = opt.poly;
         delete opt.poly;
+        let { width, miter } = poly._svg || {};
         this.add_item({
             type: "polygon",
-            width: poly.width,
-            miter: poly.miter,
+            width,
+            miter,
             selected: true,
             ...Object.assign({}, { center: {x:0, y:0, z:0} }, opt),
             ...poly.toObject()