Clear undo stack when first opening native editor (#39003)

* Add regression test for #35344

* Clear undo's when first opening editor

* Make sure normal undo's still work

e2e/test/scenarios/native/reproductions/35344-undo-in-native-editor-goes-to-far.cy.spec.js

+import { restore, focusNativeEditor } from "e2e/support/helpers";
+
+const questionDetails = {
+  name: "REVIEWS SQL",
+  native: { query: "select REVIEWER from REVIEWS" },
+};
+
+describe("issue 35344", () => {
+  beforeEach(() => {
+    restore();
+    cy.signInAsNormalUser();
+  });
+
+  it("should not allow the user to undo to the empty editor (metabase#35344)", () => {
+    cy.createNativeQuestion(questionDetails, { visitQuestion: true });
+
+    cy.findByTestId("query-builder-main").findByText("Open Editor").click();
+
+    // make sure normal undo still works
+    focusNativeEditor().type("--");
+    expect(focusNativeEditor().findByText("--")).to.exist;
+
+    focusNativeEditor().type("{meta}z");
+    focusNativeEditor().findByText("--").should("not.exist");
+
+    // more undoing does not change to empty editor
+    focusNativeEditor().type("{meta}z");
+    expect(focusNativeEditor().findByText("select")).to.exist;
+  });
+});

frontend/src/metabase/query_builder/components/NativeQueryEditor/NativeQueryEditor.tsx

@@ -422,6 +422,9 @@ export class NativeQueryEditor extends Component<
     this.handleQueryUpdate(query?.queryText() ?? "");
     editor.renderer.setScrollMargin(SCROLL_MARGIN, SCROLL_MARGIN, 0, 0);
 
+    // reset undo manager to prevent undoing to empty editor
+    editor.getSession().getUndoManager().reset();
+
     // hmmm, this could be dangerous
     if (!this.props.readOnly) {
       editor.focus();