Ping or open an object's asset from its hierarchy row (#353)

The asset link in the inspector already pings an asset on a click and
opens it on a double-click. The rows of the Scene objects panel only
selected and folded. Now they lead to the asset the same way.

- A click on the row that is selected already pings the object's
  asset in the asset panel. The selection stays. The ping comes on
  release, so picking a row up to drag it pings nothing.
- A double-click or Enter on an object's row opens its asset,
  selected or not.
- ListView has a new onReselect for a plain click on the row that is
  selected alone. onSelect stays quiet then, as nothing changes.

Decided without asking:
- A double-click on an object's row no longer folds it. The chevron
  and the arrow keys still do. A group's row has no asset and keeps
  folding on a double-click.
- A click with Ctrl or Shift, and one that narrows a multi-selection
  to its row, does not ping. Both change the selection.
- A row whose asset is missing pings and opens nothing.

Findings:
- The double-click window goes by time (400 ms), not by the event's
  detail. Two quick click() calls from the harness are a double-click.
  The comment in e2e 01 said otherwise and is gone.

Tests:
- e2e 01 (melektaus-atx): ALL PASSED, 13 checks. The two checks for
  folding on a double-click became one for the ping and two for
  opening. Counter-check without the ping: that check red.
- Gate (melektaus-atx): CHECK EXIT 0, 268 files, 4142 tests.
- Not checked: Enter on a row, a group's row on a double-click.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ui/widgets/ListView.ts

@@ -93,6 +93,8 @@ interface DragState {
   spot: DropSpot | null;
   /** Pressed inside a multi-selection: a release that never travelled narrows it to this row. */
   narrows: boolean;
+  /** Pressed on the row that was selected alone already: a release that never travelled reselects it. */
+  reselects: boolean;
 }
 
 /**
@@ -109,6 +111,11 @@ export class ListView extends Widget {
   private contextId: string | null = null;
   onSelect?: (id: string | null, modifiers?: PickModifiers) => void;
   onActivate?: (id: string) => void;
+  /**
+   * A plain click on the row that is selected already – `onSelect` stays quiet then, as nothing
+   * changes. In a list whose rows can be dragged it comes on release, so picking a row up is not it.
+   */
+  onReselect?: (id: string) => void;
   /** Returning the opened menu keeps its row marked for as long as it is up. */
   onContextMenu?: (id: string, globalX: number, globalY: number) => Popup | void;
   /** A right-click on the empty space below the rows or on a heading, which have no menu of their own. */
@@ -349,6 +356,7 @@ export class ListView extends Widget {
       // A press inside a multi-selection keeps it, so the selection is still there while dragging;
       // only a plain click (see `onDragEnd`) narrows it down to this row.
       const narrows = this.highlighted.size > 1 && this.highlighted.has(item.id);
+      const reselects = !narrows && item.id === this.selectedId;
       const dragged = Boolean(this.onDrop || this.onDragOut);
       if (narrows && !dragged) this.pick(item.id);
       else if (!narrows && !this.onDragOut && (!this.highlighted.has(item.id) || item.id === this.selectedId))
@@ -362,8 +370,9 @@ export class ListView extends Widget {
           active: false,
           spot: null,
           narrows,
+          reselects,
         };
-      }
+      } else if (reselects) this.onReselect?.(item.id);
     }
   }
 
@@ -411,6 +420,7 @@ export class ListView extends Widget {
     if (!drag?.active) {
       // The press never travelled, so it was a click after all – now it may select.
       if (drag?.narrows) this.pick(drag.id);
+      else if (drag?.reselects) this.onReselect?.(drag.id);
       else if (drag && this.onDragOut) this.select(drag.id);
       return;
     }