Add mpsc channel between live receive and push loops so hashes
received from a peer aren't pushed right back (echo prevention).
Change initial reconciliation to use tokio::join! for concurrent
send/receive, avoiding QUIC flow-control deadlock when both sides
have large transfers. Update known_hashes to union-insert so
peer-received hashes persist across poll cycles.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Jason Tudisco
ccce1474d4