fix(frontend): valid scalar markup + selector/truncated coverage in ResultsPanel

- Replace invalid role="strong" with data-testid="scalar-value"
- Add test (d): selecting "tutti" re-fetches preview with the large limit
- Render "(risultati troncati)" indicator when truncated; assert in test (a)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/viewers/ResultsPanel.test.tsx

@@ -30,7 +30,7 @@ test("(a) renders grid cells for a 2×2 preview result", async () => {
           ["Bob", 25],
         ],
         execution_ms: 5,
-        truncated: false,
+        truncated: true,
         limit: 10,
         offset: 0,
       })
@@ -46,7 +46,10 @@ test("(a) renders grid cells for a 2×2 preview result", async () => {
   expect(screen.getByText("25")).toBeInTheDocument();
 
   // Grid must be present, not bold scalar
-  expect(screen.queryByRole("strong")).not.toBeInTheDocument();
+  expect(screen.queryByTestId("scalar-value")).not.toBeInTheDocument();
+
+  // truncated:true → show the "risultati troncati" indicator
+  expect(screen.getByText(/risultati troncati/i)).toBeInTheDocument();
 });
 
 // (b) 1×1 preview → bold scalar shown, no grid
@@ -67,7 +70,7 @@ test("(b) renders bold scalar for a 1×1 result", async () => {
   render(wrap(<ResultsPanel sessionId="sess-2" />));
 
   // Should show the scalar value in bold
-  const bold = await screen.findByRole("strong");
+  const bold = await screen.findByTestId("scalar-value");
   expect(bold).toHaveTextContent("42");
 
   // No grid
@@ -107,3 +110,36 @@ test("(c) Esporta CSV button calls the export endpoint", async () => {
 
   await waitFor(() => expect(exportCalled).toBe(true));
 });
+
+// (d) selecting "tutti" drives sqlPreview with the large/unlimited limit
+test("(d) selecting tutti re-fetches preview with the large limit", async () => {
+  const limits: unknown[] = [];
+
+  server.use(
+    http.post(`${BASE}/sessions/sess-4/sql/preview`, async ({ request }) => {
+      const body = (await request.json()) as { limit?: number };
+      limits.push(body.limit);
+      return HttpResponse.json({
+        columns: ["id"],
+        rows: [[1], [2]],
+        execution_ms: 3,
+        truncated: false,
+        limit: body.limit ?? 10,
+        offset: 0,
+      });
+    })
+  );
+
+  const user = userEvent.setup();
+  render(wrap(<ResultsPanel sessionId="sess-4" />));
+
+  // Initial fetch uses limit 10
+  await waitFor(() => expect(limits).toContain(10));
+
+  // Select "tutti"
+  const select = screen.getByLabelText(/righe da visualizzare/i);
+  await user.selectOptions(select, "tutti");
+
+  // A re-fetch with the large/unlimited limit must occur
+  await waitFor(() => expect(limits.some((l) => (l as number) > 10)).toBe(true));
+});

frontend/src/viewers/ResultsPanel.tsx

@@ -64,14 +64,17 @@ export function ResultsPanel({ sessionId }: Props) {
 
       {/* Scalar result: 1 col × 1 row → bold value */}
       {data && isScalar && (
-        <strong role="strong">{String(data.rows[0][0])}</strong>
+        <strong data-testid="scalar-value">{String(data.rows[0][0])}</strong>
       )}
 
       {/* Grid for everything else */}
       {data && !isScalar && (
-        <div className="ag-theme-alpine" style={{ height: 400, width: "100%" }}>
-          <AgGridReact columnDefs={columnDefs} rowData={rowData} />
-        </div>
+        <>
+          <div className="ag-theme-alpine" style={{ height: 400, width: "100%" }}>
+            <AgGridReact columnDefs={columnDefs} rowData={rowData} />
+          </div>
+          {data.truncated && <div>(risultati troncati)</div>}
+        </>
       )}
     </div>
   );