perf(scene): make geometry edits incremental

Avoid full document, cache, and GPU rebuilds for entity deltas so add, delete, history, selection, and live polyline edits stay responsive on large drawings.

src/app/commands/layerprops.rs

@@ -129,9 +129,14 @@ impl OpenCADStudio {
                                 self.push_undo_snapshot(i, "LAYER COLOR");
                                 self.tabs[i].dirty = true;
                                 // By-layer colour is baked into every wire on
-                                // this layer — re-tessellate so they repaint
-                                // immediately (issue #231 class).
-                                self.tabs[i].scene.bump_geometry();
+                                // this layer. The dependency index maps block
+                                // children back to their top-level INSERTs, so
+                                // unrelated entities stay warm.
+                                self.tabs[i]
+                                    .scene
+                                    .invalidate_layer_dependencies(std::slice::from_ref(
+                                        &layer_name,
+                                    ));
                                 self.command_line.push_output(&format!(
                                     "LAYER: '{}' color set to ACI {}.",
                                     layer_name, idx