feat(FN-4552): complete Step 1 — fix desktop files button handler

Fusion-Task-Id: FN-4552
Fusion-Task-Lineage: dad48f2c-25a8-4fca-8f00-16307936621c

packages/dashboard/app/components/Header.tsx

@@ -1523,7 +1523,7 @@ export function Header({
         {!isCompact && onOpenFiles && (
           <button
             className={`btn-icon${filesOpen ? " btn-icon--active" : ""}`}
-            onClick={onOpenFiles}
+            onClick={() => onOpenFiles()}
             title="Browse files"
             data-testid="files-toggle-btn"
           >

packages/dashboard/app/components/__tests__/Header.test.tsx

@@ -113,6 +113,16 @@ describe("Header", () => {
     expect(onOpenSettings).toHaveBeenCalled();
   });
 
+  it("calls onOpenFiles with zero arguments from desktop files button", () => {
+    const onOpenFiles = vi.fn();
+    renderHeader({ onOpenFiles }, "desktop");
+
+    fireEvent.click(screen.getByTestId("files-toggle-btn"));
+
+    expect(onOpenFiles).toHaveBeenCalledTimes(1);
+    expect(onOpenFiles.mock.calls[0]).toEqual([]);
+  });
+
   it("calls onOpenGitHubImport when import button is clicked", () => {
     const onOpenGitHubImport = vi.fn();
     renderHeader({ onOpenGitHubImport });