Fix findUsages/undo/node-lookup bugs, split Viewport and Editor, share command and inspector helpers

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/editor/actions.ts

@@ -2,9 +2,12 @@
  * Editor actions that several places trigger the same way (inspector, hierarchy context
  * menu, keyboard): they run the command and put the selection where the user expects it.
  */
+import { DeleteAssetCommand } from '../core/commands/assetCommands';
 import { AddColliderCommand } from '../core/commands/colliderCommands';
 import { CreateContainerCommand } from '../core/commands/containerCommands';
 import { RemoveSceneObjectsCommand } from '../core/commands/sceneObjectCommands';
+import { findAsset, findUsages } from '../core/model/Project';
+import { Dialog } from '../ui';
 import { type EditorState, objectSelection } from './state';
 
 /** Groups the objects into a new container asset placed in their stead; selects the container. */
@@ -27,3 +30,26 @@ export function addCollider(state: EditorState, sceneId: string, objectId: strin
 export function removeObjects(state: EditorState, sceneId: string, objectIds: readonly string[]): boolean {
   return state.execute(new RemoveSceneObjectsCommand(sceneId, objectIds));
 }
+
+/**
+ * Asks before deleting an asset, spelling out what goes with it. Both ways of deleting (the
+ * asset list's context menu and the Delete key) go through here, so the warning cannot differ
+ * depending on how the user triggered it.
+ */
+export function confirmDeleteAsset(state: EditorState, assetId: string): void {
+  const asset = findAsset(state.project, assetId);
+  if (!asset) return;
+  const usages = findUsages(state.project, assetId).length;
+  const detail =
+    asset.type === 'scene'
+      ? `The scene and its ${asset.objects.length} object(s) are removed.`
+      : usages === 0
+        ? 'This cannot be undone with Ctrl+Z after reload.'
+        : asset.type === 'container'
+          ? `${usages} placed container(s) are removed together with their content.`
+          : `${usages} placed instance(s) are removed as well (scenes and container templates).`;
+  new Dialog(`Delete "${asset.name}"?`, detail, [
+    { label: 'Cancel' },
+    { label: 'Delete', danger: true, onClick: () => state.execute(new DeleteAssetCommand(assetId)) },
+  ]).openCentered();
+}