Extract useGoogleAuth from app.tsx

docs/APP_REFACTORING_DESIGN.md

@@ -100,7 +100,7 @@ We will gradually eliminate React state variables in `src/app.tsx` and derive th
 *   [x] **Step 3.4:** Extract `config` state. Parse display settings on render using `argsToConfig` helper. Remove state. In `ViewPage`, run `updateChartWithConfig(config, data)` synchronously during the render pass (e.g. in the `useMemo` that derives query parameters/config) to update the in-memory chart data before it is rendered by the `<Chart>` child component. Run E2E and visual tests to verify no rendering regressions occurred.
 
 #### Phase 4: Structural Page Nesting
-*   [ ] **Step 4.1:** Create `src/hooks/use_google_auth.ts` to manage Google Drive authentication token updates. Remove `hasGoogleToken` state from `src/app.tsx`.
+*   [x] **Step 4.1:** Create `src/hooks/use_google_auth.ts` to manage Google Drive authentication token updates. Remove `hasGoogleToken` state from `src/app.tsx`.
 *   [ ] **Step 4.2:** Create `src/pages/view_page.tsx` containing layout rendering (`renderMainArea`), asynchronous data loaders, view state management, `revokeObjectUrls` cleanups, and `<GoogleAuthModal>` error fallback state and rendering.
 *   [ ] **Step 4.3:** Create `src/pages/intro_page.tsx` rendering the landing screen and its own local header.
 *   [ ] **Step 4.4:** Refactor `src/app.tsx` to serve as a pure routing switch routing to `<IntroPage />` or `<ViewPage />`. In `App`, handle Google Drive redirection synchronously during the render pass by returning a `<Navigate replace />` element (preventing render flashing), and ensure the redirection parser checks both the router `location.search` and the external `window.location.search` to handle HashRouter query structure robustly. Once external parameters (like `state` or `authcode`) are detected, they must be stripped from `window.location.search` using `window.history.replaceState` to prevent redirection loops on page refresh. Remove all layout state logic from the root file, including moving the `useWebMcpBridge` hook invocation into `<ViewPage />`. Run final verification scripts (`npm run check:all`).