Opus pre-release advisor MUST-FIX patched inline:
- api/routes.py:7290-7308 _handle_folder_download: add Connection: close
header before end_headers() to satisfy HTTP/1.1 framing on the on-the-fly
ZIP stream. Without it, post-#2836 protocol_version bump leaves clients
hanging waiting for the next pipelined response after central-directory
bytes finish. Opus verified this is the ONLY streaming response #2836
missed — all other paths (j/t helpers, 12 hand-written responses, 8 SSE
endpoints, auth flow) are already correctly framed.