Fix disconnect detection: TX/RX loops set running=false on EOF

When a TCP connection closes (EOF or write error), the loop now sets
the shared running flag to false, which stops the status report loop
and all other tasks. Adds "test ended" log messages.

The TCP multi-conn "MikroTik shows 0 on send" is a separate issue
requiring TCP-level status exchange (MikroTik sends 12-byte status
messages on TCP connections, not just a data stream).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server.rs

@@ -377,6 +377,7 @@ async fn run_tcp_multiconn_server(streams: Vec<TcpStream>, cmd: Command) -> Resu
     state.running.store(false, Ordering::SeqCst);
     for h in tx_handles { let _ = h.await; }
     for h in rx_handles { let _ = h.await; }
+    tracing::info!("TCP multi-connection test ended");
     Ok(())
 }
 
@@ -395,6 +396,7 @@ async fn tcp_tx_loop(
 
     while state.running.load(Ordering::Relaxed) {
         if writer.write_all(&packet).await.is_err() {
+            state.running.store(false, Ordering::SeqCst);
             break;
         }
         state.tx_bytes.fetch_add(tx_size as u64, Ordering::Relaxed);
@@ -425,7 +427,10 @@ async fn tcp_rx_loop(mut reader: tokio::net::tcp::OwnedReadHalf, state: Arc<Band
     let mut buf = vec![0u8; 65536];
     while state.running.load(Ordering::Relaxed) {
         match reader.read(&mut buf).await {
-            Ok(0) | Err(_) => break,
+            Ok(0) | Err(_) => {
+                state.running.store(false, Ordering::SeqCst);
+                break;
+            }
             Ok(n) => {
                 state.rx_bytes.fetch_add(n as u64, Ordering::Relaxed);
             }