test: campaign characterization (7 tests)

- src/testHelpers.js: renderApp, createCampaignViaUI, selectCampaignByName
- App.characterization.test.js: createCampaign, addCharacter, updateCharacter, deleteCharacter, deleteCampaign + path namespace + bg url
- mock firestore writeBatch sync (was async, app no-await)

Locks path + payload shape per action. Refactor guard.

src/testHelpers.js

@@ -0,0 +1,37 @@
+// test helpers: drive App UI to states. Used across characterization suites.
+import React from 'react';
+import { render, screen, fireEvent, waitFor } from '@testing-library/react';
+import App from './App';
+import { MOCK_DB } from './__mocks__/firebase/_mock-db';
+
+// Render app, wait for auth + campaign list.
+export async function renderApp() {
+  window.history.replaceState({}, '', '/');
+  global.alert = jest.fn();
+  window.open = jest.fn();
+  const utils = render(<App />);
+  await waitFor(() => screen.getByRole('button', { name: /Create Campaign/i }));
+  return utils;
+}
+
+// Open create-campaign modal, fill name, submit. Returns campaign id from recorded call.
+export async function createCampaignViaUI(name = 'Test Campaign') {
+  fireEvent.click(screen.getByRole('button', { name: /Create Campaign/i }));
+  await waitFor(() => screen.getByLabelText(/Campaign Name/i));
+  fireEvent.change(screen.getByLabelText(/Campaign Name/i), { target: { value: name } });
+  fireEvent.click(screen.getByRole('button', { name: /^Create$/i }));
+  // wait for setDoc recorded
+  const { getCalls } = require('./__mocks__/firebase/_mock-db');
+  await waitFor(() => getCalls().find(c => c.fn === 'setDoc' && c.path.includes('/campaigns/')));
+  const call = getCalls().find(c => c.fn === 'setDoc' && c.path.includes('/campaigns/'));
+  return call.path.split('/').pop(); // campaign id
+}
+
+// Click campaign card by name to select it. Returns selected campaign id.
+export async function selectCampaignByName(name) {
+  const card = await waitFor(() => screen.getByText(name));
+  fireEvent.click(card);
+  await waitFor(() => screen.getByText(/Managing:/i));
+}
+
+export { MOCK_DB };