Chart builder: discoverable entry points — Build Chart door, dataset picker, no-datasets state

src/app/components/ChartBuilderModal.test.tsx

@@ -80,7 +80,7 @@ describe('ChartBuilderModal', () => {
       await Promise.resolve();
     });
 
-    expect(container.textContent).toContain('Building from');
+    expect(container.textContent).toContain('Nums'); // the dataset picker names the data
     expect(container.textContent).toContain('scatter'); // the guidance hint rendered
   });
 
@@ -155,12 +155,33 @@ describe('ChartBuilderModal', () => {
     vi.useRealTimers();
   });
 
-  test('shows the empty state when no dataset is loaded', async () => {
+  test('shows the no-datasets empty state with its one next step (3D)', async () => {
     await act(async () => {
       root.render(<ChartBuilderModal />);
       await Promise.resolve();
     });
-    expect(container.textContent).toContain('No dataset loaded');
+    expect(container.textContent).toContain('No datasets yet');
+    const action = Array.from(container.querySelectorAll('button')).find(
+      (b) => b.textContent === 'Add a dataset',
+    );
+    expect(action).toBeDefined();
+  });
+
+  test('offers a dataset chooser when datasets exist but none is loaded', async () => {
+    const ds = createDataset({
+      name: 'Waiting',
+      data: [{ a: 1 }],
+      format: 'json',
+      source: 'inline',
+      now: T,
+    });
+    useDatasetStore.getState().add(ds);
+
+    await act(async () => {
+      root.render(<ChartBuilderModal />);
+      await Promise.resolve();
+    });
+    expect(container.textContent).toContain('Choose a dataset');
   });
 
   test('a complete filter row reaches the renderer as a top-level transform (1C)', async () => {