test: add proxyWidgets reordering tests

Add tests documenting that:
- Direct reordering of proxyWidgets tuples preserves all entries
- Widget references remain correct after reorder
- The activeWidgets round-trip is lossy when nodes are unresolvable

Amp-Thread-ID: https://ampcode.com/threads/T-019c73f9-0348-715e-9ef1-f6add8677e27

src/core/graph/subgraph/proxyWidget.test.ts

@@ -125,6 +125,88 @@ describe('Subgraph proxyWidgets', () => {
     subgraphNode.widgets[0].computedHeight = 10
     expect(subgraphNode.widgets[0].value).toBe('value')
   })
+  describe('proxyWidgets reordering', () => {
+    test('reordering proxyWidgets directly preserves all entries', () => {
+      const [subgraphNode, innerNodes] = setupSubgraph(2)
+      innerNodes[0].addWidget('text', 'widgetA', 'valueA', () => {})
+      innerNodes[1].addWidget('text', 'widgetB', 'valueB', () => {})
+
+      subgraphNode.properties.proxyWidgets = [
+        ['1', 'widgetA'],
+        ['2', 'widgetB']
+      ]
+      expect(subgraphNode.widgets).toHaveLength(2)
+
+      const proxyWidgets = parseProxyWidgets(
+        subgraphNode.properties.proxyWidgets
+      )
+      const [first, second] = proxyWidgets
+      subgraphNode.properties.proxyWidgets = [second, first]
+
+      expect(subgraphNode.properties.proxyWidgets).toStrictEqual([
+        ['2', 'widgetB'],
+        ['1', 'widgetA']
+      ])
+      expect(subgraphNode.widgets).toHaveLength(2)
+    })
+
+    test('reordering maintains correct widget references after swap', () => {
+      const [subgraphNode, innerNodes] = setupSubgraph(2)
+      innerNodes[0].addWidget('text', 'widgetA', 'valueA', () => {})
+      innerNodes[1].addWidget('text', 'widgetB', 'valueB', () => {})
+
+      subgraphNode.properties.proxyWidgets = [
+        ['1', 'widgetA'],
+        ['2', 'widgetB']
+      ]
+      expect(subgraphNode.widgets[0].value).toBe('valueA')
+      expect(subgraphNode.widgets[1].value).toBe('valueB')
+
+      const proxyWidgets = parseProxyWidgets(
+        subgraphNode.properties.proxyWidgets
+      )
+      subgraphNode.properties.proxyWidgets = [proxyWidgets[1], proxyWidgets[0]]
+
+      expect(subgraphNode.widgets[0].value).toBe('valueB')
+      expect(subgraphNode.widgets[1].value).toBe('valueA')
+    })
+
+    test('activeWidgets round-trip drops unresolvable widgets', () => {
+      const [subgraphNode, innerNodes] = setupSubgraph(2)
+      innerNodes[0].addWidget('text', 'widgetA', 'valueA', () => {})
+      innerNodes[1].addWidget('text', 'widgetB', 'valueB', () => {})
+
+      subgraphNode.properties.proxyWidgets = [
+        ['1', 'widgetA'],
+        ['2', 'widgetB']
+      ]
+      expect(subgraphNode.widgets).toHaveLength(2)
+
+      // Simulate the lossy activeWidgets getter: resolving [nodeId, widgetName]
+      // tuples by looking up nodes/widgets. If a node is missing, it returns [].
+      const subgraph = subgraphNode.subgraph
+      function mapWidgets([id, name]: [string, string]) {
+        const wNode = subgraph._nodes_by_id[id]
+        if (!wNode?.widgets) return []
+        const widget = wNode.widgets.find((w) => w.name === name)
+        if (!widget) return []
+        return [[wNode, widget]]
+      }
+
+      // Remove a node to make it unresolvable
+      subgraph.remove(innerNodes[0])
+
+      const proxyWidgets = parseProxyWidgets(
+        subgraphNode.properties.proxyWidgets
+      )
+      const resolved = proxyWidgets.flatMap(mapWidgets)
+
+      // The lossy round-trip drops the entry for the removed node
+      expect(resolved).toHaveLength(1)
+      expect(proxyWidgets).toHaveLength(2)
+    })
+  })
+
   test('Prevents duplicate promotion', () => {
     const [subgraphNode, innerNodes] = setupSubgraph(1)
     innerNodes[0].addWidget('text', 'stringWidget', 'value', () => {})