address greptile review feedback (greploop iteration 4)

- Add guard assertion before non-null click on custom code switch
- Use await act(async ...) for timer advancement to avoid act warnings
- Pin locale in date range assertion for CI determinism

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/litellm-dashboard/src/components/EntityUsageExport/ExportSummary.test.tsx

@@ -14,8 +14,10 @@ describe("ExportSummary", () => {
 
   it("should display formatted date range", () => {
     render(<ExportSummary dateRange={dateRange} selectedFilters={[]} />);
-    const text = screen.getByText(/\d+.*-.*\d+/);
-    expect(text).toBeInTheDocument();
+    // Pin locale to en-US so test is deterministic regardless of CI runner locale
+    const expectedFrom = dateRange.from!.toLocaleDateString("en-US");
+    const expectedTo = dateRange.to!.toLocaleDateString("en-US");
+    expect(screen.getByText(`${expectedFrom} - ${expectedTo}`)).toBeInTheDocument();
   });
 
   it("should show singular 'filter' for one filter", () => {

ui/litellm-dashboard/src/components/GuardrailsMonitor/GuardrailConfig.test.tsx

@@ -54,7 +54,10 @@ describe("GuardrailConfig", () => {
       customCodeSwitch = container.querySelector('[role="switch"]');
       container = container.parentElement;
     }
-    await user.click(customCodeSwitch!);
+    if (!customCodeSwitch) {
+      throw new Error("Could not find the Custom Code Override switch via DOM traversal");
+    }
+    await user.click(customCodeSwitch);
     expect(screen.getByPlaceholderText(/async def evaluate/)).toBeInTheDocument();
   });
 
@@ -82,7 +85,7 @@ describe("GuardrailConfig", () => {
     const user = userEvent.setup({ advanceTimers: vi.advanceTimersByTime });
     render(<GuardrailConfig {...defaultProps} />);
     await user.click(screen.getByRole("button", { name: /re-run on failing logs/i }));
-    act(() => { vi.advanceTimersByTime(2500); });
+    await act(async () => { vi.advanceTimersByTime(2500); });
     expect(screen.getByText(/7\/10 would now pass/)).toBeInTheDocument();
   });