fix bounding box update for model changes. add menu for it

src/mesh/build.js

@@ -191,6 +191,7 @@ function ui_build() {
             h.button({ _: 'analyze', disabled: true }),
             h.button({ _: 'repair', onclick: api.tool.repair }),
             h.div({ class: "vsep" }),
+            h.button({ _: 'bounds', onclick() { api.selection.boundsBox({toggle:true}) } }),
             h.button({ _: 'gridlines', onclick() { api.grid() } }),
             h.button({ _: 'wireframe', onclick() { api.wireframe() } }),
         ]),

src/mesh/model.js

@@ -227,6 +227,11 @@ mesh.model = class MeshModel extends mesh.object {
             this.removed = 'complete';
         }
     }
+
+    updateBoundsBox() {
+        mesh.util.defer(this.group.deferUBB);
+    }
+
 };
 
 })();

src/mesh/object.js

@@ -20,6 +20,7 @@ mesh.object = class MeshObject {
 
     constructor(id) {
         this.id = id || mesh.util.uuid();
+        this.deferUBB = () => { this.updateBoundsBox() };
         worker.object_create({id: this.id, type: this.type});
     }