test: exercise migrated workflow offline

tests/test_service_worker.py

@@ -40,7 +40,7 @@ const cache = {{
     state.puts.push(key);
     state.migrated.push(key);
     state.activationOrder.push('put:' + key);
-    storedResponses.set(key, response.clone());
+    storedResponses.set(new URL(key, 'https://forge.example').href, response.clone());
   }},
 }};
 const oldCache = {{
@@ -1080,20 +1080,27 @@ def test_offline_activation_migrates_cached_optional_feature_before_deleting_old
   state.failedAdds = [asset];
   context.self.__testOptionalFeatures.push(asset);
   await dispatch('activate');
-  process.stdout.write(JSON.stringify(state));
+  state.failFetch = true;
+  const response = await dispatch('fetch', {
+    method: 'GET', mode: 'cors',
+    url: 'https://forge.example/dashboard/feature-issue-capture-test.js',
+  });
+  process.stdout.write(JSON.stringify({ body: await response.text(), state }));
 """
     )
 
-    assert result["migrated"] == [
+    assert result["body"] == "previous cached feature"
+    state = result["state"]
+    assert state["migrated"] == [
         "/dashboard/feature-issue-capture-test.js"
     ]
-    assert result["individuallyAdded"] == []
-    assert "/dashboard/feature-issue-capture-test.js" not in result["addAttempts"]
-    assert result["activationOrder"] == [
+    assert state["individuallyAdded"] == []
+    assert "/dashboard/feature-issue-capture-test.js" not in state["addAttempts"]
+    assert state["activationOrder"] == [
         "put:/dashboard/feature-issue-capture-test.js",
         "delete:stackchain-dashboard-old",
     ]
-    assert result["claimed"] is True
+    assert state["claimed"] is True
 
 
 def test_activate_warms_optional_features_without_blocking_siblings_or_claim():