fix(test): use AppState['openFiles'][number] instead of a nonexistent module

The test imported OpenFile from shared/editor-types, which does not exist. Vitest
passed because a type-only import is erased at runtime; CI typecheck caught it.
I had run tsc before adding this file and never re-ran it.

src/renderer/src/store/slices/worktrees/teardown/worktree-teardown-array-identity.test.ts

@@ -1,8 +1,9 @@
 import { describe, expect, it } from 'vitest'
 import type { AppState } from '../../../types'
-import type { OpenFile } from '../../../../../../shared/editor-types'
 import { applyRemoveWorktreeSuccessState } from './remove-worktree-store-cleanup'
 
+type OpenFile = AppState['openFiles'][number]
+
 const REMOVED = 'repo-1::/repos/one/removed'
 const KEPT = 'repo-1::/repos/one/kept'