feat: upgrade toolchain and soften sync recovery after network blips

Bump Vite 8, matrix-js-sdk, and related deps; fix immer/vanilla-extract imports for new majors. Replace blocking sync error dialog with background recovery on wake/offline, and disable Vite auto-open in dev. Add feature handoff documentation index.

src/app/features/common-settings/permissions/PermissionGroups.tsx

@@ -2,7 +2,7 @@
 import React, { useCallback, useEffect, useMemo, useState } from 'react';
 import { Badge, Box, Button, Chip, config, Menu, Spinner, Text } from 'folds';
 import { Icon, Icons } from '../../../components/icons';
-import produce from 'immer';
+import { produce } from 'immer';
 import { SequenceCard } from '../../../components/sequence-card';
 import { SequenceCardStyle } from '../styles.css';
 import { SettingTile } from '../../../components/setting-tile';