test(web): add missing resolveTheme branch test for malformed theme URI (ATB-53)

apps/web/src/lib/__tests__/theme-resolution.test.ts

···
     expect(result.tokens).toEqual(FALLBACK_THEME.tokens);
   });
 
+  it("returns FALLBACK_THEME when defaultLightThemeUri is malformed (parseRkeyFromUri returns null)", async () => {
+    mockFetch.mockResolvedValueOnce(
+      policyResponse({ defaultLightThemeUri: "malformed-uri" })
+    );
+    const result = await resolveTheme(APPVIEW, undefined, undefined);
+    expect(result.tokens).toEqual(FALLBACK_THEME.tokens);
+    // Only one fetch should happen (policy only — no theme fetch)
+    expect(mockFetch).toHaveBeenCalledTimes(1);
+  });
+
   it("returns FALLBACK_THEME when theme fetch fails", async () => {
     mockFetch
       .mockResolvedValueOnce(policyResponse())