Show numeric sub-variation edge values as bare numbers

Numeric dependsOn values (merge-type variations) are RFC edge values,
not ATTR names. Display them as the number, not as "ATTR: N" or
"subvariation N".

static/components/PaneSubObjects.js

@@ -40,9 +40,13 @@ export const PaneSubObjects = {
                     ...node.labelSpecs.map(ls => ({
                         kind: 'label_spec', node: ls, label: ls.label ?? '(no label)',
                     })),
-                    ...node.subvariations.map((sv, idx) => ({
-                        kind: 'variation', node: sv, label: `subvariation ${idx + 1}`,
-                    })),
+                    ...node.subvariations.map((sv, idx) => {
+                        const dep = sv.dependsOn;
+                        const label = dep == null ? `subvariation ${idx + 1}`
+                            : isNaN(Number(dep)) ? `ATTR: ${dep}`
+                            : String(dep);
+                        return { kind: 'variation', node: sv, label, hasChildren: true };
+                    }),
                 ];
             }
             if (node.type === 'bar') {