Update src/containers/sb3-downloader.jsx

src/containers/sb3-downloader.jsx

@@ -97,13 +97,17 @@ class SB3Downloader extends React.Component {
             return;
         }
         try {
-            const handle = await FileSystemAPI.showSaveFilePicker(this.props.projectFilename);
-            await this.saveToHandle(handle);
-            this.props.onSetFileHandle(handle);
-            const title = getProjectTitleFromFilename(handle.name);
-            if (title) {
-                this.props.onSetProjectTitle(title);
-            }
+          // 外部でも使用できるようにプロパティに保存
+          this.handle = {
+              name: this.props.projectFilename
+          };
+          this.title = getProjectTitleFromFilename(this.handle.name);
+          if (this.title) {
+              this.props.onSetProjectTitle(this.title);
+          }
+
+          await this.saveToBlobAndDownload();
+
         } catch (e) {
             this.handleSaveError(e);
         }
@@ -121,6 +125,42 @@ class SB3Downloader extends React.Component {
         }
         return this.saveAsNew();
     }
+    async saveToBlobAndDownload () {
+        if (!this.props.canSaveProject) return;
+
+        this.startedSaving();
+
+        // Blob を生成
+        const chunks = [];
+        const jszipStream = this.props.saveProjectSb3Stream();
+
+        await new Promise((resolve, reject) => {
+            jszipStream.on('data', chunk => chunks.push(chunk));
+            jszipStream.on('end', resolve);
+            jszipStream.on('error', reject);
+        });
+
+        const blob = new Blob(chunks, { type: 'text/plain' }); // ← ここを text/plain に変更
+
+        // 拡張子が .txt であることを保証
+        let filename = this.handle.name;
+        if (!filename.endsWith('.txt')) {
+            filename = filename.replace(/\.[^/.]+$/, '') + '.txt';
+        }
+
+        // ダウンロードリンクを作成
+        const a = document.createElement('a');
+        const url = URL.createObjectURL(blob);
+        a.href = url;
+        a.download = filename;
+        document.body.appendChild(a);
+        a.click();
+        document.body.removeChild(a);
+        URL.revokeObjectURL(url);
+
+        this.finishedSaving();
+    }
+
     async saveToHandle (handle) {
         if (!this.props.canSaveProject) {
             return;