refactor(frontend): Reactivityで型を明示するように (#12791)

* refactor(frontend): Reactivityで型を明示するように

* fix: プロパティの参照が誤っているのを修正

* fix: 初期化の値を空配列に書き換えていた部分をnullに置き換え

packages/frontend/src/pages/drive.vue

@@ -11,11 +11,12 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <script lang="ts" setup>
 import { computed, ref } from 'vue';
+import * as Misskey from 'misskey-js';
 import XDrive from '@/components/MkDrive.vue';
 import { i18n } from '@/i18n.js';
 import { definePageMetadata } from '@/scripts/page-metadata.js';
 
-const folder = ref(null);
+const folder = ref<Misskey.entities.DriveFolder | null>(null);
 
 const headerActions = computed(() => []);