Problem

Receive-pack’s report-status response does not use side-band-64k framing. Some strict git clients expect sideband-wrapped status when they advertise the capability, and may fail or misparse the response.

Impact

• Push status reporting may break with certain git client versions
• Progress messages during push processing cannot be streamed to the client
• Capability is advertised but not fully implemented

Acceptance Criteria

• Report-status wrapped in side-band-64k when client requests it
• Progress/error messages sent on sideband channels 2 and 3
• Interop test: git push with verbose output shows server progress
• Backward compatible: plain report-status still works without sideband