fix(test): give async image-insert store mocks the openFiles list (#25357)

#25176 and #24489 landed together and collided in
insertRichMarkdownImageFromPath. #25176 added three test files whose
@/store mock returns { settings, folderWorkspaces, worktreesByRepo }.
#24489 made the same function look up the open document with
state.openFiles.find(...) to pass document-folder access to the import.
Under the mock, openFiles is undefined, so the lookup throws, the catch
shows "Failed to insert image", and no image is inserted -- 38 tests
fail on main.

The real store always carries openFiles, so production behavior of both
PRs is intact; the mocks were just written against the pre-#24489 shape.
Add openFiles: [] to the three mocks.

src/renderer/src/components/editor/rich-markdown-async-image-paste.test.ts

@@ -17,7 +17,12 @@ vi.mock('@/runtime/runtime-file-client', () => ({ importExternalPathsToRuntime:
 vi.mock('@/lib/connection-context', () => ({ getConnectionId: vi.fn(() => null) }))
 vi.mock('@/store', () => ({
   useAppStore: {
-    getState: vi.fn(() => ({ settings: null, folderWorkspaces: [], worktreesByRepo: {} }))
+    getState: vi.fn(() => ({
+      settings: null,
+      folderWorkspaces: [],
+      worktreesByRepo: {},
+      openFiles: []
+    }))
   }
 }))
 vi.mock('@/runtime/runtime-rpc-client', () => ({

src/renderer/src/components/editor/rich-markdown-async-image-table.test.ts

@@ -11,7 +11,12 @@ vi.mock('@/runtime/runtime-file-client', () => ({ importExternalPathsToRuntime:
 vi.mock('@/lib/connection-context', () => ({ getConnectionId: vi.fn(() => null) }))
 vi.mock('@/store', () => ({
   useAppStore: {
-    getState: vi.fn(() => ({ settings: null, folderWorkspaces: [], worktreesByRepo: {} }))
+    getState: vi.fn(() => ({
+      settings: null,
+      folderWorkspaces: [],
+      worktreesByRepo: {},
+      openFiles: []
+    }))
   }
 }))
 vi.mock('@/runtime/runtime-rpc-client', () => ({

src/renderer/src/components/editor/useLocalImagePick.test.tsx

@@ -13,7 +13,12 @@ vi.mock('@/runtime/runtime-file-client', () => ({ importExternalPathsToRuntime:
 vi.mock('@/lib/connection-context', () => ({ getConnectionId: vi.fn(() => null) }))
 vi.mock('@/store', () => ({
   useAppStore: {
-    getState: vi.fn(() => ({ settings: null, folderWorkspaces: [], worktreesByRepo: {} }))
+    getState: vi.fn(() => ({
+      settings: null,
+      folderWorkspaces: [],
+      worktreesByRepo: {},
+      openFiles: []
+    }))
   }
 }))
 vi.mock('@/runtime/runtime-rpc-client', () => ({