barGroupKey: strip final same-class char run, no ID parsing

static/components/PaneSubObjects.js

@@ -2,12 +2,11 @@ import { h } from 'vue';
 import { ObjectShort } from './ObjectShort.js';
 import { getKindGroups } from '../subobject-kinds.js';
 
-// Extract the P?L? fragment as a visual grouping key.
-// Falls back to stripping trailing digits if the pattern is absent,
-// which yields singleton groups — not a crash, just no visual grouping.
+// Strip the final maximal run of same-class characters (all-digits or all-non-digits)
+// from the ID tail. Everything before that run is the group key.
 function barGroupKey(id) {
-    const m = id.match(/P\d+L\d+/);
-    return m ? m[0] : id.replace(/\d+$/, '');
+    const m = id.match(/(\d+|\D+)$/);
+    return m ? id.slice(0, m.index) : id;
 }
 
 export const PaneSubObjects = {