// ctx.getFile() returns the server-side path only — not the original filename
file = await ctx.getFile();
// file.file_path = "documents/file_<server-id>.pdf"  <- server-side path, NOT original

// msg.document.file_name is available here but never read
const saved = await downloadAndSaveTelegramFile(file.file_path, fetchImpl);
//   msg.document?.file_name is ignored

const headerFileName = parseContentDispositionFileName(res.headers.get("content-disposition"));
// -> null: Telegram's download server sends no Content-Disposition header

let fileName = headerFileName || fileNameFromUrl || path.basename(filePathHint);
// fileNameFromUrl = path.basename(".../documents/file_<server-id>.pdf")
// -> "file_<server-id>.pdf"  <- server-side name, not the original

// originalFilename = "file_<server-id>.pdf" (server-side name wrongly treated as original)
const base = path.parse(originalFilename).name;  // -> "file_<server-id>"
const sanitized = sanitizeFilename(base);
id = `${sanitized}---${uuid}${ext}`;
// Final saved name: "file_<server-id>---<new-uuid>.pdf"
// Double-UUID pattern — original name (e.g., "business-plan.docx") is gone

// Step 1: Update downloadAndSaveTelegramFile to accept an optional name override
const downloadAndSaveTelegramFile = async (filePath, fetchImpl, telegramFileName) => {
    const fetched = await fetchRemoteMedia({ ... });
    const originalName = telegramFileName ?? fetched.fileName ?? filePath;
    return saveMediaBuffer(fetched.buffer, fetched.contentType, "inbound", maxBytes, originalName);
};

// Step 2: Pass msg.document.file_name at the call site
const originalFileName = msg.document?.file_name ?? msg.audio?.file_name ?? msg.video?.file_name;
const saved = await downloadAndSaveTelegramFile(file.file_path, fetchImpl, originalFileName);