Dashboard editor undo: ⌘Z / ⇧⌘Z over a 50-entry history of commits, folding keystrokes and the grid's own correction as the flow editor does

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

frontend/tests/editor.spec.ts

@@ -11,6 +11,8 @@ import { api, apiPage, deleteAll } from "./utils/api"
  *
  * The third is what a widget drawn without its title is dragged by, since the
  * header it used to be dragged by is the thing that is gone.
+ *
+ * The last is the undo a mis-click needs: a removed widget comes back.
  */
 
 const dashboardName = `test_editor_${Date.now().toString(36)}`
@@ -201,3 +203,25 @@ test("a palette is pasted as a link and read as roles", async ({ page }) => {
     "",
   )
 })
+
+test("a removed widget comes back on undo and goes again on redo", async ({
+  page,
+}) => {
+  await openEditor(page)
+  const frames = page.getByTestId("widget-frame")
+  const top = frames.filter({ hasText: "Top" })
+
+  await top.click()
+  await page.getByTestId("delete-widget").click()
+  await expect(top).toHaveCount(0)
+
+  // Removing closes the panel, so the keys reach the canvas rather than a
+  // field, which keeps its own undo.
+  await page.keyboard.press("ControlOrMeta+z")
+  await expect(top).toBeVisible()
+  await expect(frames).toHaveCount(2)
+
+  await page.keyboard.press("ControlOrMeta+Shift+z")
+  await expect(top).toHaveCount(0)
+  await expect(frames).toHaveCount(1)
+})