fix(subgraph): trust persisted previewExposures, stop re-auto-exposing on load

Auto-exposed previews would reappear after reload even when the user had
explicitly hidden them. The host's `properties.previewExposures` already
captures user intent, but `LGraph.configure` was unconditionally running
`autoExposeKnownPreviewNodes` after hydration, second-guessing the
serialized state.

- Gate `autoExposeKnownPreviewNodes` on `properties.previewExposures`
  being undefined. A node that has never been saved (or comes from a
  pre-PR workflow with no `previewExposures` property) still gets the
  convenience auto-expose pass; once the property exists in any form,
  including an empty array, the serialized state is authoritative.
- Always serialize `previewExposures` (including as `[]` when empty)
  so "user cleared everything" is distinguishable from "never touched".

Amp-Thread-ID: https://ampcode.com/threads/T-019e4671-bc67-7039-b6c6-9f5b11a07e42
Co-authored-by: Amp <amp@ampcode.com>

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

@@ -28,6 +28,7 @@ vi.mock('@/services/litegraphService', () => ({
 
 import {
   CANVAS_IMAGE_PREVIEW_WIDGET,
+  autoExposeKnownPreviewNodes,
   demoteWidget,
   getPromotableWidgets,
   hasUnpromotedWidgets,
@@ -341,6 +342,74 @@ describe('promoteRecommendedWidgets', () => {
   })
 })
 
+describe('autoExposeKnownPreviewNodes', () => {
+  beforeEach(() => {
+    setActivePinia(createTestingPinia({ stubActions: false }))
+    updatePreviewsMock.mockReset()
+  })
+
+  it('auto-exposes previews when host has no persisted previewExposures property', () => {
+    const subgraph = createTestSubgraph()
+    const subgraphNode = createTestSubgraphNode(subgraph)
+    const glslNode = new LGraphNode('GLSLShader')
+    glslNode.type = 'GLSLShader'
+    subgraph.add(glslNode)
+
+    autoExposeKnownPreviewNodes(subgraphNode)
+
+    expect(
+      usePreviewExposureStore().getExposures(
+        subgraphNode.rootGraph.id,
+        String(subgraphNode.id)
+      )
+    ).toHaveLength(1)
+  })
+
+  it('does not auto-expose when host has empty persisted previewExposures (user cleared)', () => {
+    const subgraph = createTestSubgraph()
+    const subgraphNode = createTestSubgraphNode(subgraph)
+    subgraphNode.properties.previewExposures = []
+    const glslNode = new LGraphNode('GLSLShader')
+    glslNode.type = 'GLSLShader'
+    subgraph.add(glslNode)
+
+    autoExposeKnownPreviewNodes(subgraphNode)
+
+    expect(
+      usePreviewExposureStore().getExposures(
+        subgraphNode.rootGraph.id,
+        String(subgraphNode.id)
+      )
+    ).toEqual([])
+  })
+
+  it('does not auto-expose when host has non-empty persisted previewExposures', () => {
+    const subgraph = createTestSubgraph()
+    const subgraphNode = createTestSubgraphNode(subgraph)
+    const glslNode = new LGraphNode('GLSLShader')
+    glslNode.type = 'GLSLShader'
+    subgraph.add(glslNode)
+    const otherNode = new LGraphNode('OtherShader')
+    otherNode.type = 'GLSLShader'
+    subgraph.add(otherNode)
+    subgraphNode.properties.previewExposures = [
+      {
+        name: CANVAS_IMAGE_PREVIEW_WIDGET,
+        sourceNodeId: String(otherNode.id),
+        sourcePreviewName: CANVAS_IMAGE_PREVIEW_WIDGET
+      }
+    ]
+
+    autoExposeKnownPreviewNodes(subgraphNode)
+
+    expect(
+      usePreviewExposureStore()
+        .getExposures(subgraphNode.rootGraph.id, String(subgraphNode.id))
+        .map((e) => e.sourceNodeId)
+    ).not.toContain(String(glslNode.id))
+  })
+})
+
 describe('hasUnpromotedWidgets', () => {
   beforeEach(() => {
     setActivePinia(createTestingPinia({ stubActions: false }))

src/core/graph/subgraph/promotionUtils.ts

@@ -470,6 +470,7 @@ function nodeWidgets(n: LGraphNode): WidgetItem[] {
 }
 
 export function autoExposeKnownPreviewNodes(subgraphNode: SubgraphNode): void {
+  if (subgraphNode.properties.previewExposures !== undefined) return
   const { updatePreviews } = useLitegraphService()
   const interiorNodes = subgraphNode.subgraph.nodes
   for (const node of interiorNodes) {

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

@@ -1031,13 +1031,9 @@ export class SubgraphNode extends LGraphNode implements BaseLGraph {
       rootGraphId,
       hostLocator
     )
-    if (previewExposures.length > 0) {
-      serializedProperties.previewExposures = previewExposures.map((entry) => ({
-        ...entry
-      }))
-    } else {
-      delete serializedProperties.previewExposures
-    }
+    serializedProperties.previewExposures = previewExposures.map((entry) => ({
+      ...entry
+    }))
 
     const quarantine = parseProxyWidgetErrorQuarantine(
       this.properties.proxyWidgetErrorQuarantine

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

@@ -1175,12 +1175,12 @@ describe('SubgraphWidgetPromotion', () => {
           expected: [named12, named14]
         },
         {
-          name: 'omits previewExposures when the store has no entries for the host',
+          name: 'writes empty previewExposures when the store has no entries for the host',
           addExposures: [],
           staleProperty: [
             { name: 'stale', sourceNodeId: '0', sourcePreviewName: CANVAS }
           ],
-          expected: undefined,
+          expected: [],
           expectLiveUnchanged: true
         }
       ]