fix(ui): remove redundant newlines in Gemini messages (#18538)

packages/cli/src/test-utils/render.tsx

@@ -122,6 +122,9 @@ const configProxy = new Proxy({} as Config, {
       return () =>
         '/Users/test/project/foo/bar/and/some/more/directories/to/make/it/long';
     }
+    if (prop === 'getUseBackgroundColor') {
+      return () => true;
+    }
     const internal = getMockConfigInternal();
     if (prop in internal) {
       // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion