fix(desktop): buffer appimagetool download before writing to disk

Bun.write(path, Response) silently fails on GitHub Actions CI runners,
causing the AppImage packaging to complete without actually creating the
AppImage file. Switch to downloading the full response body as an
ArrayBuffer first, then writing the buffer to disk.

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

Author: Vrtak-CZ

apps/desktop/scripts/package-appimage.ts

@@ -200,7 +200,11 @@ exec "\${HERE}/../lib/klovi/bin/launcher" "$@"
   if (!response.ok) {
     fail(`Failed to download appimagetool: ${response.status} ${response.statusText}`);
   }
-  await Bun.write(toolPath, response);
+  // Use arrayBuffer() to fully download before writing — streaming a Response
+  // directly via Bun.write() can silently fail on some CI environments.
+  const toolBytes = await response.arrayBuffer();
+  console.log(`  Downloaded ${toolBytes.byteLength} bytes`);
+  await Bun.write(toolPath, toolBytes);
   await run(["chmod", "+x", toolPath]);
 
   // 9. Build the AppImage