Fix P2/P3 review findings: DNR redirect format, runtime type guard, cache test setup

packages/extension/tests/setup.ts

@@ -0,0 +1,28 @@
+const mockStorage: Record<string, unknown> = {};
+
+const chromeMock = {
+  storage: {
+    local: {
+      set: async (data: Record<string, unknown>) => {
+        Object.assign(mockStorage, data);
+      },
+      get: async (key: string | string[]) => {
+        if (Array.isArray(key)) {
+          const result: Record<string, unknown> = {};
+          for (const k of key) result[k] = mockStorage[k];
+          return result;
+        }
+        return { [key]: mockStorage[key] };
+      },
+      remove: async (key: string | string[]) => {
+        const keys = Array.isArray(key) ? key : [key];
+        for (const k of keys) delete mockStorage[k];
+      },
+      clear: async () => {
+        Object.keys(mockStorage).forEach((k) => delete mockStorage[k]);
+      },
+    },
+  },
+};
+
+(global as any).chrome = chromeMock;