Multiselection and container assets: create container from selection, template instances

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/editor/panels/AssetPanel.ts

@@ -5,9 +5,9 @@ import { ASSET_TYPES, type AssetType } from '../../core/model/AssetTypes';
 import type { Vec2 } from '../../core/model/Properties';
 import { findAsset, findUsages } from '../../core/model/Project';
 import { Button, Dialog, ListView, Menu, type MenuItem, Panel, ScrollContainer } from '../../ui';
-import type { EditorState } from '../state';
+import { type EditorState, objectSelection } from '../state';
 
-const TYPE_LABELS: Record<AssetType, string> = { scene: 'Scene', camera: 'Camera', sprite: 'Sprite', behavior: 'Behavior', collider: 'Collider' };
+const TYPE_LABELS: Record<AssetType, string> = { scene: 'Scene', camera: 'Camera', sprite: 'Sprite', behavior: 'Behavior', collider: 'Collider', container: 'Container' };
 
 /** Lists all assets of the project; creates, places and deletes them. */
 export class AssetPanel extends Panel {
@@ -77,7 +77,7 @@ export class AssetPanel extends Panel {
       return;
     }
     const command = new PlaceAssetCommand(scene.id, assetId, this.placementPoint());
-    if (this.state.execute(command)) this.state.select({ kind: 'object', sceneId: scene.id, objectId: command.objectId });
+    if (this.state.execute(command)) this.state.select(objectSelection(scene.id, [command.objectId]));
   }
 
   private openContextMenu(id: string, x: number, y: number): void {
@@ -100,7 +100,9 @@ export class AssetPanel extends Panel {
     const detail =
       asset.type === 'scene'
         ? `The scene and its ${asset.objects.length} object(s) are removed.`
-        : usages > 0
+        : asset.type === 'container' && usages > 0
+          ? `${usages} placed container(s) are removed from scenes together with their content.`
+          : usages > 0
           ? `${usages} placed instance(s) are removed from scenes as well.`
           : 'This cannot be undone with Ctrl+Z after reload.';
     new Dialog(`Delete "${asset.name}"?`, detail, [