feat: compose App shell with Toolbar, Editor and ODT export button

src/App.svelte

@@ -0,0 +1,63 @@
+<script lang="ts">
+  import type { Editor } from '@tiptap/core';
+  import EditorComponent from './lib/editor/Editor.svelte';
+  import Toolbar from './lib/editor/Toolbar.svelte';
+  import { exportToOdt } from './lib/export/odt';
+
+  let editor: Editor | null = $state(null);
+
+  async function handleExport() {
+    if (editor) await exportToOdt(editor);
+  }
+</script>
+
+<main>
+  <header>
+    <Toolbar {editor} />
+    <button class="export-btn" onclick={handleExport} disabled={!editor}>
+      Download .odt
+    </button>
+  </header>
+  <EditorComponent bind:editor />
+</main>
+
+<style>
+  main {
+    display: flex;
+    flex-direction: column;
+    height: 100%;
+  }
+
+  header {
+    display: flex;
+    align-items: center;
+    background: var(--color-toolbar-bg);
+    border-bottom: 1px solid var(--color-border);
+    box-shadow: var(--shadow);
+  }
+
+  .export-btn {
+    margin-left: auto;
+    margin-right: 1rem;
+    padding: 0.4rem 1rem;
+    background: var(--color-primary);
+    color: white;
+    border: none;
+    border-radius: var(--radius);
+    font-size: 0.85rem;
+    font-family: var(--font-sans);
+    font-weight: 500;
+    cursor: pointer;
+    white-space: nowrap;
+    transition: background 0.15s;
+  }
+
+  .export-btn:hover:not(:disabled) {
+    background: var(--color-primary-hover);
+  }
+
+  .export-btn:disabled {
+    opacity: 0.5;
+    cursor: not-allowed;
+  }
+</style>

src/main.ts

@@ -0,0 +1,7 @@
+import { mount } from 'svelte';
+import App from './App.svelte';
+import './styles/global.css';
+
+const app = mount(App, { target: document.getElementById('app')! });
+
+export default app;