fix: merge GridStackView into DashboardView (#19)

DashboardView and GridStackView rendered the same three charts from the
same hardcoded data, so every chart factory method existed twice. The
dashboard is now the GridStackLayout variant at @Route(""):

- GridStackView deleted, its grid/toolbar/chart factories moved into
  DashboardView, which keeps the point-click notifications the old
  dashboard had.
- Charts size to their widget (100%/100%) instead of a fixed 400px.
- MainLayout has one dashboard entry; nav.gridstack/page.gridstack keys
  dropped from all three bundles.
- Storage key is "dashboard" (was "gridstack-demo"), so a saved layout
  from the old route is not reused.
- GridStackViewTest renamed to DashboardViewTest, plus a test asserting
  the three charts render.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0124BiJikbhbiEsNfJxdWM69

src/test/java/com/example/views/DashboardViewTest.java

@@ -0,0 +1,121 @@
+package com.example.views;
+
+import com.example.Application;
+import com.example.components.BarChart;
+import com.example.components.GridStackItem;
+import com.example.components.GridStackLayout;
+import com.example.components.LineChart;
+import com.example.components.PieChart;
+import com.vaadin.browserless.SpringBrowserlessTest;
+import com.vaadin.browserless.ViewPackages;
+import com.vaadin.browserless.internal.ElementUtilsKt;
+import com.vaadin.flow.component.button.Button;
+import com.vaadin.flow.component.html.Div;
+import com.vaadin.flow.dom.DomEvent;
+import com.vaadin.flow.internal.JacksonUtils;
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+@SpringBootTest(classes = Application.class)
+@ViewPackages(classes = DashboardView.class)
+class DashboardViewTest extends SpringBrowserlessTest {
+
+    @Test
+    void view_rendersGridWithDefaultWidgets() {
+        navigate(DashboardView.class);
+
+        GridStackLayout grid = $view(GridStackLayout.class).first();
+        assertNotNull(grid);
+
+        List<GridStackItem.Position> layout = grid.getLayout();
+        assertEquals(4, layout.size(), "expected the four default widgets");
+        assertTrue(layout.stream().allMatch(p -> p.w() > 0 && p.h() > 0));
+    }
+
+    @Test
+    void view_rendersTheThreeCharts() {
+        navigate(DashboardView.class);
+
+        assertNotNull($view(LineChart.class).first());
+        assertNotNull($view(BarChart.class).first());
+        assertNotNull($view(PieChart.class).first());
+    }
+
+    @Test
+    void addAndCloseWidget_changesItemCount() {
+        navigate(DashboardView.class);
+
+        GridStackLayout grid = $view(GridStackLayout.class).first();
+        int initial = grid.getLayout().size();
+
+        button("gridstack.addWidget").click();
+        assertEquals(initial + 1, grid.getLayout().size());
+
+        clickCloseButton($view(GridStackItem.class).last());
+        assertEquals(initial, grid.getLayout().size());
+    }
+
+    @Test
+    void closeButton_removesTheClickedWidgetOnly() {
+        navigate(DashboardView.class);
+
+        GridStackLayout grid = $view(GridStackLayout.class).first();
+        GridStackItem first = $view(GridStackItem.class).first();
+        String closedId = first.getItemId();
+
+        clickCloseButton(first);
+
+        List<GridStackItem.Position> layout = grid.getLayout();
+        assertEquals(3, layout.size());
+        assertFalse(layout.stream().anyMatch(p -> closedId.equals(p.id())),
+                "the closed widget must be gone from the layout");
+    }
+
+    @Test
+    void closeListener_firesOnceItemIsDetached() {
+        navigate(DashboardView.class);
+
+        GridStackLayout grid = $view(GridStackLayout.class).first();
+        GridStackItem item = $view(GridStackItem.class).first();
+        int[] fired = {0};
+        item.addCloseListener(e -> fired[0]++);
+
+        item.close();
+
+        assertEquals(1, fired[0]);
+        assertEquals(3, grid.getLayout().size());
+    }
+
+    @Test
+    void nonClosableItem_hasNoCloseButton() {
+        navigate(DashboardView.class);
+
+        GridStackItem item = $view(GridStackItem.class).first();
+        assertTrue(item.isClosable(), "items are closable by default");
+
+        item.setClosable(false);
+        assertFalse(item.isClosable());
+        assertFalse(item.getChildren().anyMatch(child -> child == item.getCloseButton()));
+    }
+
+    /** Fires the DOM click the close button listens for, rather than calling
+     *  {@code close()} directly, so the button's own wiring is covered too. */
+    private void clickCloseButton(GridStackItem item) {
+        Div closeButton = item.getCloseButton();
+        ElementUtilsKt._fireDomEvent(closeButton.getElement(),
+                new DomEvent(closeButton.getElement(), "click", JacksonUtils.createObjectNode()));
+    }
+
+    private Button button(String translationKey) {
+        String caption = getCurrentView().getElement().getComponent()
+                .orElseThrow().getTranslation(translationKey);
+        return $view(Button.class).withText(caption).first();
+    }
+}