fix(ui): keep an unnamed class out of the schema removal preview, one at a time

docs/content/ui.md

@@ -986,6 +986,15 @@ how many classes narrow and states that nothing already labeled is invalidated.
 It also names what the narrowing defers: a batch still open on the outgoing version keeps
 writing the class that was dropped, and those labels block a release rather than this save.
 
+**A class that has no name yet takes neither path.** The draft may hold one - naming a
+class is typed work, and the draft exists so typed work survives - but the published
+contract refuses a blank name, so the preview refuses it too. The editor therefore keeps
+an unnamed class out of every preview body: removing one is a local edit with no request,
+and removing a *named* class while one waits for a name previews the named classes only.
+The same rule bounds how many can wait: **Add class** adds nothing while a class is still
+unnamed, and instead selects that class and says so - the remedy Save already uses for the
+same blank, not a greyed button.
+
 That does not demote the 409. Nothing is locked between a preview and the publish, so
 somebody can label a class in the gap and turn a preview that looked safe into a refusal -
 which is why the publish's own refusal stays authoritative, and why it renders through the

frontend/ui-core/src/screens/SchemaEditor.tsx

@@ -640,6 +640,16 @@ export function SchemaEditor({
 
   function addClass(): void {
     if (saveInFlight.current || preview.isPending) return;
+    // One unnamed class at a time: a second one is indistinguishable from the
+    // first, and `save` would refuse the draft anyway. Same remedy as there —
+    // land on the class that still needs a name rather than grey the button.
+    const blank = classes.findIndex((declared) => declared.name.trim() === "");
+    if (blank !== -1) {
+      setSelected(blank);
+      setFilter("");
+      toast("Name the new class first");
+      return;
+    }
     edit([...classes, { name: "", geometries: ["bbox"], color: null, attributes: [] }]);
     // Selected, and the filter cleared — a new class has an empty name, so any
     // filter at all would hide the row that was just created.
@@ -658,8 +668,17 @@ export function SchemaEditor({
 
   async function requestRemoveClass(index: number): Promise<void> {
     if (saveInFlight.current || preview.isPending) return;
+    // A class still unnamed was never published, so nothing can carry it and no
+    // preview is owed; it is also not a class `POST /preview` accepts, so it is
+    // left out of the candidate the way `save` would refuse to send it.
+    if (classes[index]?.name.trim() === "") {
+      removeClass(index);
+      return;
+    }
     setFlow({ kind: "checking-removal" });
-    const candidate = classes.filter((_, position) => position !== index);
+    const candidate = classes.filter(
+      (declared, position) => position !== index && declared.name.trim() !== "",
+    );
     try {
       const previewed = await preview.mutateAsync({ classes: candidate });
       if (previewed.is_refused) {

frontend/ui-core/src/screens/schemaDraft.test.tsx

@@ -663,6 +663,36 @@ describe("saving twice with nothing edited in between", () => {
  * merged, and a publish always carries what was actually typed, including the
  * keystroke still inside the debounce window when Save was pressed.
  */
+describe("one unnamed class at a time", () => {
+  it("refuses a second Add and lands on the class still waiting for a name", async () => {
+    render(
+      mount(
+        <>
+          <ProjectScreen projectId={PROJECT} tab="schema" />
+          <Toaster />
+        </>,
+      ),
+    );
+    await screen.findByTestId("schema-editor");
+    await userEvent.click(screen.getByTestId("add-class"));
+    await userEvent.click(screen.getByTestId("class-list").querySelectorAll("button")[0]);
+
+    await userEvent.click(screen.getByTestId("add-class"));
+
+    expect(screen.getByTestId("class-list").querySelectorAll("button")).toHaveLength(
+      CLASSES.length + 1,
+    );
+    expect(await screen.findByText("Name the new class first")).toBeDefined();
+    expect(screen.getByTestId(`class-name-${CLASSES.length}`)).toHaveProperty("value", "");
+
+    await userEvent.type(screen.getByTestId(`class-name-${CLASSES.length}`), "pedestrian");
+    await userEvent.click(screen.getByTestId("add-class"));
+    expect(screen.getByTestId("class-list").querySelectorAll("button")).toHaveLength(
+      CLASSES.length + 2,
+    );
+  });
+});
+
 describe("the draft lives on the server", () => {
   it("seeds from the server draft when there is no local one", async () => {
     curatedDrafts.set(PROJECT, {

frontend/ui-core/src/screens/screens.test.tsx

@@ -2239,6 +2239,40 @@ describe("the schema editor's two panels", () => {
     expect(screen.getByTestId("class-list").querySelectorAll("button")).toHaveLength(2);
     expect(screen.queryByTestId("class-name-1")).not.toBeNull();
   });
+
+  it("removes a class that was never named without asking the server", async () => {
+    withClasses(CLASSES);
+    render(mount(<ProjectScreen projectId={PROJECT} tab="schema" />));
+    await screen.findByTestId("class-list");
+    await userEvent.click(screen.getByTestId("add-class"));
+    const before = sent.filter((request) => request.url.endsWith("/schema/preview")).length;
+
+    await userEvent.click(screen.getByTestId("remove-class-2"));
+
+    await waitFor(() =>
+      expect(screen.getByTestId("class-list").querySelectorAll("button")).toHaveLength(2),
+    );
+    expect(sent.filter((request) => request.url.endsWith("/schema/preview"))).toHaveLength(before);
+    expect(screen.queryByTestId("schema-preview-error")).toBeNull();
+  });
+
+  it("leaves an unnamed class out of the removal preview it cannot be part of", async () => {
+    withClasses(CLASSES);
+    render(mount(<ProjectScreen projectId={PROJECT} tab="schema" />));
+    await screen.findByTestId("class-list");
+    await userEvent.click(screen.getByTestId("add-class"));
+
+    await userEvent.click(screen.getByTestId("class-list").querySelectorAll("button")[1]);
+    await userEvent.click(screen.getByTestId("remove-class-1"));
+
+    await waitFor(() =>
+      expect(screen.getByTestId("class-list").querySelectorAll("button")).toHaveLength(2),
+    );
+    const request = sent.find((sentRequest) => sentRequest.url.endsWith("/schema/preview"));
+    if (request === undefined) throw new Error("Expected a schema preview request");
+    expect(JSON.parse(bodies.get(request) ?? "")).toEqual({ classes: [CLASSES[0]] });
+    expect(screen.queryByTestId("schema-preview-error")).toBeNull();
+  });
 });
 
 describe("the project view's sections", () => {