fix(fig): finalize worker cleanup semantics

- Retain worker graphs only for lazy first-page imports\n- Make termination idempotent\n- Wait on deterministic population telemetry in E2E coverage

packages/core/src/kiwi/fig/parse/worker.ts

@@ -60,10 +60,11 @@ self.onmessage = (event: MessageEvent<WorkerRequest>) => {
     const { nodeChanges, blobs, images, figKiwiVersion, figSchemaDeflated } = parseFigBuffer(
       parseRequest.buffer
     )
-    graph = importNodeChanges(nodeChanges, blobs, new Map(images), parseRequest.options)
-    graph.figKiwiVersion = figKiwiVersion
-    graph.figSchemaDeflated = figSchemaDeflated
-    const serialized = serializeSceneGraph(graph)
+    const parsedGraph = importNodeChanges(nodeChanges, blobs, new Map(images), parseRequest.options)
+    parsedGraph.figKiwiVersion = figKiwiVersion
+    parsedGraph.figSchemaDeflated = figSchemaDeflated
+    graph = parseRequest.options?.populate === 'first-page' ? parsedGraph : undefined
+    const serialized = serializeSceneGraph(parsedGraph)
     const transfer =
       parseRequest.options?.populate === 'first-page'
         ? []

packages/core/src/kiwi/fig/population/client.ts

@@ -78,6 +78,7 @@ function createPopulationWorkerClient(graph: SceneGraph, worker: Worker): FigPop
   >()
   let revision = 0
   let stale = false
+  let disposed = false
   let applyingDelta = false
   const invalidate = () => {
     if (applyingDelta || stale) return
@@ -161,6 +162,8 @@ function createPopulationWorkerClient(graph: SceneGraph, worker: Worker): FigPop
       })
     },
     terminate() {
+      if (disposed) return
+      disposed = true
       emitTelemetry({ event: 'terminated' })
       fail(false)
     }

tests/e2e/pages/fig-population-worker.spec.ts

@@ -23,15 +23,20 @@ test('populates a real lazy FIG page in the retained parse worker', async () =>
   })
   if (!targetPageId) throw new Error('Target page not found')
 
-  const loading = editor.page.getByTestId('canvas-loading')
-  const switchPromise = editor.page.evaluate((pageId) => {
+  await editor.page.evaluate((pageId) => {
     const store = window.openPencil?.getStore?.()
     if (!store) throw new Error('OpenPencil store not initialized')
     return store.switchPage(pageId)
   }, targetPageId)
-  await expect(loading).toBeVisible()
-  await switchPromise
-  await expect(loading).not.toBeVisible()
+  await expect
+    .poll(() =>
+      editor.page.evaluate(() =>
+        (Reflect.get(window, 'figPopulationWorkerEvents') as Array<{ event: string }>).some(
+          ({ event }) => event === 'populate'
+        )
+      )
+    )
+    .toBe(true)
 
   const currentPage = await editor.page.evaluate(() => {
     const store = window.openPencil?.getStore?.()