Detect hoster error-page downloads (<512 B) and trigger retry

Some hosters return tiny error responses (e.g. 9 bytes) with HTTP 200.
- downloadToFile: detect files <512 B, log content, delete and throw for retry
- Post-download: catch <512 B files even when totalBytes is unknown
- Logs the error-page content for debugging

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "real-debrid-downloader",
-  "version": "1.4.81",
+  "version": "1.4.82",
   "description": "Real-Debrid Downloader Desktop (Electron + React + TypeScript)",
   "main": "build/main/main/main.js",
   "author": "Sucukdeluxe",

src/main/download-manager.ts

@@ -3437,6 +3437,7 @@ export class DownloadManager extends EventEmitter {
           // A real archive part or video file should be at least 1 KB.
           const tooSmall = expectsNonEmptyFile && (
             fileSizeOnDisk <= 0
+            || fileSizeOnDisk < 512
             || (item.totalBytes && item.totalBytes > 10240 && fileSizeOnDisk < 1024)
           );
           if (tooSmall) {
@@ -4106,6 +4107,24 @@ export class DownloadManager extends EventEmitter {
           }
         }
 
+        // Detect tiny error-response files (e.g. hoster returning "Forbidden" with HTTP 200).
+        // No legitimate file-hoster download is < 512 bytes.
+        if (written > 0 && written < 512) {
+          let snippet = "";
+          try {
+            snippet = await fs.promises.readFile(effectiveTargetPath, "utf8");
+            snippet = snippet.slice(0, 200).replace(/[\r\n]+/g, " ").trim();
+          } catch { /* ignore */ }
+          logger.warn(`Tiny download erkannt (${written} B): "${snippet}"`);
+          try {
+            await fs.promises.rm(effectiveTargetPath, { force: true });
+          } catch { /* ignore */ }
+          this.dropItemContribution(active.itemId);
+          item.downloadedBytes = 0;
+          item.progressPercent = 0;
+          throw new Error(`Download zu klein (${written} B) – Hoster-Fehlerseite?${snippet ? ` Inhalt: "${snippet}"` : ""}`);
+        }
+
         item.downloadedBytes = written;
         item.progressPercent = item.totalBytes ? Math.max(0, Math.min(100, Math.floor((written / item.totalBytes) * 100))) : 100;
         item.speedBps = 0;