fix(peer): log disconnect cause; bind e2e browse listener on all interfaces

The brokered third-party browse e2e failed deterministically on CI. The test
bound its listener to 127.0.0.1 only, but the server brokers back the address
it observed for that client - the host's routable IP (172.17.0.2 under Docker,
10.x on a CI runner). The sharer's dial was refused, it fell back to
re-brokering, and the accept never arrived. The sibling third-party browse
tests already bind 0.0.0.0.

disconnect_with_error logged only "disconnect" and dropped the io::Error on the
floor, which is what made this invisible in the logs; it now logs the cause.

soulseek-rs-lib/src/actor/peer_actor.rs

@@ -609,7 +609,10 @@ impl PeerActor {
 
     fn disconnect_with_error(&mut self, error: Error) {
         let username = self.peer_username();
-        debug!("[peer:{}] disconnect", username);
+        // Include the cause: a failed outbound dial reports nothing else, so
+        // without it an unreachable peer is indistinguishable from a clean
+        // disconnect in the logs.
+        debug!("[peer:{}] disconnect: {}", username, error);
 
         self.stream.take();
 

soulseek-rs-lib/tests/e2e.rs

@@ -1528,8 +1528,13 @@ fn a_third_party_client_browses_our_shares_via_the_server_broker() {
 
     // The third-party client listens and advertises its port, then asks the
     // server to broker a P connection from the sharer.
+    //
+    // Bind every interface, not just loopback: the server brokers back the
+    // address it observed for this client, which is the host's routable IP
+    // (172.17.0.2 under Docker, 10.x on a CI runner), not 127.0.0.1. A
+    // loopback-only listener refuses that dial and the browse never arrives.
     let listener =
-        std::net::TcpListener::bind("127.0.0.1:0").expect("browser listener");
+        std::net::TcpListener::bind("0.0.0.0:0").expect("browser listener");
     let browser_port = listener.local_addr().unwrap().port();
     let server_addr = format!("{}:{}", server.host, server.port);
     let mut srv = login_raw(&server_addr, "e2e_qt_brok_browser", "pw")