The 1680-line server.rs is split:
- handshake.rs: perform_auth_handshake helper + close_with_auth_failed + auth tests
+ start_auth_listener / close_listener_auth_failed test helpers + AuthListenerResult enum
- server.rs: crdt_sync_handler (now invokes perform_auth_handshake) + wait_for_sync_text
+ broadcast/e2e/keepalive tests
Auth handshake (Steps 1-3 of the WebSocket handshake) is a self-contained sequence
that takes &mut SplitSink + &mut SplitStream and returns Option<AuthMessage>. The
caller observes None to mean the connection has already been closed with the
appropriate close code.
No behaviour change. All 63 crdt_sync tests pass; full suite green.
dave
0e09a1ed4b