Implement hash verification for flash file

          const blob = await this.download(file.path, (value, total) => {

            onDownloadProgress(value, total, file.name);

          });

          // Simple zip integrity check: fetch "<path>.sha256sum" and compare.

          try {

            const expected = await this.fetchChecksum(`${file.path}.sha256sum`);

            const actual = await this.computeSha256(blob);

            if (expected && actual !== expected) {

              throw new Error(

                `Checksum mismatch for ${file.name}: expected ${expected} got ${actual}`,

              );

            }

          } catch (checksumError) {

            throw new Error(

              `Checksum verification failed for ${file.name}: ${checksumError.message || checksumError}`,

            );

          }

          if (file.unzip) {

            const zipReader = new ZipReader(new BlobReader(blob));

            const filesEntries = await zipReader.getEntries();

    return filename;

  }

  async fetchChecksum(url) {

    const res = await ky.get(url);

    if (!res.ok) {

      throw new Error(`Cannot fetch checksum (${res.status})`);

    }

    const body = (await res.text()).trim();

    const match = body.match(/[a-fA-F0-9]{64}/);

    if (!match) {

      throw new Error("Invalid checksum content");

    }

    return match[0].toLowerCase();

  }

  async computeSha256(blob) {

    const buffer = await blob.arrayBuffer();

    const hashBuffer = await crypto.subtle.digest("SHA-256", buffer);

    const hashArray = Array.from(new Uint8Array(hashBuffer));

    return hashArray.map((b) => b.toString(16).padStart(2, "0")).join("");

  }

  /**

   * @param name

   * @returns {<blob>}