fix: prevent nested SubgraphNode input slots from doubling on reload (#10187)

## Summary

- Fix nested SubgraphNode input slots doubling on each page reload
- Root cause: during configure, `_configureSubgraph` recreates
`SubgraphInput` objects with new references, and the `input-added` event
handler used `===` identity check which failed for these new objects,
causing `addInput()` to duplicate inputs
- Add `id`-based fallback matching in the `input-added` handler and
rebind `_subgraphSlot` with re-registered listeners

## Changes

**`SubgraphNode.ts:614-622`**: Add UUID `id` fallback to the `===`
reference check in the `input-added` event handler. When a stale
reference is matched by id, call `_addSubgraphInputListeners()` to
update `_subgraphSlot` and re-register listeners on the new
`SubgraphInput` object.

**`SubgraphNode.test.ts`**: 2 regression tests for nested subgraph
reconfigure scenarios.

## Test plan

- [x] Existing SubgraphNode tests pass (6 passed, 34 skipped)
- [x] New tests verify inputs don't duplicate after single and repeated
reconfigure cycles
- [x] Manual: create a subgraph containing another subgraph node, save,
reload — input slots should remain unchanged

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10187-fix-prevent-nested-SubgraphNode-input-slots-from-doubling-on-reload-3266d73d3650817286abea52365a626e)
by [Unito](https://www.unito.io)

src/lib/litegraph/src/subgraph/SubgraphNode.test.ts

@@ -698,6 +698,55 @@ describe('SubgraphNode duplicate input pruning (#9977)', () => {
   })
 })
 
+describe('Nested SubgraphNode duplicate input prevention', () => {
+  it('should not duplicate inputs when the referenced subgraph is reconfigured', () => {
+    setActivePinia(createTestingPinia({ stubActions: false }))
+
+    const subgraph = createTestSubgraph({
+      inputs: [
+        { name: 'a', type: 'STRING' },
+        { name: 'b', type: 'NUMBER' }
+      ]
+    })
+
+    const node = createTestSubgraphNode(subgraph)
+    expect(node.inputs).toHaveLength(2)
+
+    // Simulate what happens during nested subgraph configure:
+    // B.configure() calls _configureSubgraph(), which recreates SubgraphInput
+    // objects and dispatches 'input-added' events with new references.
+    const serialized = subgraph.asSerialisable()
+    subgraph.configure(serialized)
+
+    // The SubgraphNode's event listener should recognize existing inputs
+    // by ID and NOT add duplicates.
+    expect(node.inputs).toHaveLength(2)
+    expect(node.inputs.every((i) => i._subgraphSlot)).toBe(true)
+  })
+
+  it('should not accumulate inputs across multiple reconfigure cycles', () => {
+    setActivePinia(createTestingPinia({ stubActions: false }))
+
+    const subgraph = createTestSubgraph({
+      inputs: [
+        { name: 'x', type: 'IMAGE' },
+        { name: 'y', type: 'VAE' }
+      ]
+    })
+
+    const node = createTestSubgraphNode(subgraph)
+    expect(node.inputs).toHaveLength(2)
+
+    for (let i = 0; i < 5; i++) {
+      const serialized = subgraph.asSerialisable()
+      subgraph.configure(serialized)
+    }
+
+    expect(node.inputs).toHaveLength(2)
+    expect(node.inputs.map((i) => i.name)).toEqual(['x', 'y'])
+  })
+})
+
 describe('SubgraphNode promotion view keys', () => {
   it('distinguishes tuples that differ only by colon placement', () => {
     setActivePinia(createTestingPinia({ stubActions: false }))

src/lib/litegraph/src/subgraph/SubgraphNode.ts

@@ -612,9 +612,14 @@ export class SubgraphNode extends LGraphNode implements BaseLGraph {
         const subgraphInput = e.detail.input
         const { name, type } = subgraphInput
         const existingInput = this.inputs.find(
-          (input) => input._subgraphSlot === subgraphInput
+          (input) =>
+            input._subgraphSlot === subgraphInput ||
+            (input._subgraphSlot && input._subgraphSlot.id === subgraphInput.id)
         )
         if (existingInput) {
+          // Rebind to the new SubgraphInput object and re-register listeners
+          // (configure recreates SubgraphInput objects with the same id)
+          this._addSubgraphInputListeners(subgraphInput, existingInput)
           const linkId = subgraphInput.linkIds[0]
           if (linkId === undefined) return