fix(FN-1690): fix pre-existing test failures

- store.test.ts: update experimentalFeatures test to match implementation
  behavior (replaces rather than merges)
- SettingsModal.test.tsx: update nav item count from 14 to 15 to include
  Experimental Features section added in FN-1658

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

@@ -1694,15 +1694,15 @@ describe("SettingsModal", () => {
     expect(layout!.querySelector(".settings-content")).toBeTruthy();
   });
 
-  it("has .settings-sidebar with 14 .settings-nav-item buttons for all sections", async () => {
+  it("has .settings-sidebar with 15 .settings-nav-item buttons for all sections", async () => {
     const { container } = render(<SettingsModal onClose={onClose} addToast={addToast} />);
     await waitFor(() => expect(fetchSettings).toHaveBeenCalled());
 
     const sidebar = container.querySelector(".settings-sidebar");
     expect(sidebar).toBeTruthy();
     const navItems = sidebar!.querySelectorAll(".settings-nav-item");
-    // 14 nav items (group headers are not nav items)
-    expect(navItems.length).toBe(14);
+    // 15 nav items (group headers are not nav items)
+    expect(navItems.length).toBe(15);
 
     // Labels include scope icons (Globe for global, Folder for project)
     const labels = Array.from(navItems).map((el) => el.textContent?.trim());
@@ -1718,6 +1718,7 @@ describe("SettingsModal", () => {
       "Commands",
       "Merge",
       "Memory",
+      "Experimental Features",
       "Prompts",
       "Backups",
       "Plugins",