fix(layers): protect locked entities

Keep locked-layer objects selectable for inspection while suppressing grips, property edits, command mutations, and stale editor writes.

src/scene/entity.rs

@@ -327,6 +327,9 @@ impl Scene {
     #[cfg_attr(target_arch = "wasm32", allow(dead_code))]
     pub fn update_entity(&mut self, mut entity: EntityType) -> bool {
         let handle = entity.common().handle;
+        if self.is_layer_locked(handle) {
+            return false;
+        }
         let Some(existing) = self.document.get_entity(handle) else {
             return false;
         };