refactor: convert openAsBlob to async function and inline implementation

Co-authored-by: streamich <[email protected]>

Author: Copilot

src/node/volume.ts

@@ -1446,29 +1446,18 @@ export class Volume implements FsCallbackApi, FsSynchronousApi {
   public statfsSync: FsSynchronousApi['statfsSync'] = notImplemented;
   /** @todo Implement statfs */
   public statfs: FsCallbackApi['statfs'] = notImplemented;
-  private readonly _openAsBlob = (filename: string, options: opts.IOpenAsBlobOptions = {}): Blob => {
+  public openAsBlob = async (path: PathLike, options?: opts.IOpenAsBlobOptions): Promise<Blob> => {
+    const filename = pathToFilename(path);
     const link = this._core.getResolvedLinkOrThrow(filename, 'open');
     const node = link.getNode();
     if (node.isDirectory()) throw createError(ERROR_CODE.EISDIR, 'open', link.getPath());
 
     const buffer = node.getBuffer();
-    const type = options.type || '';
+    const type = options?.type || '';
 
     return new Blob([buffer], { type });
   };
 
-  public openAsBlob = (path: PathLike, options?: opts.IOpenAsBlobOptions): Promise<Blob> => {
-    return new Promise((resolve, reject) => {
-      try {
-        const filename = pathToFilename(path);
-        const blob = this._openAsBlob(filename, options);
-        resolve(blob);
-      } catch (err) {
-        reject(err);
-      }
-    });
-  };
-
   private readonly _opendir = (filename: string, options: opts.IOpendirOptions): Dir => {
     const link: Link = this._core.getResolvedLinkOrThrow(filename, 'scandir');
     const node = link.getNode();