feat(SerialConsolePage): enhance echo handling by implementing an echo queue to suppress self-echoes

src/app/components/SerialConsolePage.tsx

@@ -12,6 +12,7 @@ export default function SerialConsolePage({ onBack }: Props) {
   const termRef      = useRef<Terminal | null>(null);
   const fitRef       = useRef<FitAddon | null>(null);
   const lineBuffer   = useRef('');
+  const echoQueue    = useRef<string[]>([]);
   const { status, send, subscribe } = useWs();
 
   // Keep a stable ref to `send` so the xterm onData closure never goes stale
@@ -50,9 +51,11 @@ export default function SerialConsolePage({ onBack }: Props) {
     term.onData((data) => {
       for (const char of data) {
         if (char === '\r' || char === '\n') {
-          term.write('\r\n');
+          const line = lineBuffer.current + '\r';
-          sendRef.current(lineBuffer.current + '\r');
           lineBuffer.current = '';
+          term.write('\r\n');
+          echoQueue.current.push(line);
+          sendRef.current(line);
         } else if (char === '\x7f' || char === '\b') {
           if (lineBuffer.current.length > 0) {
             lineBuffer.current = lineBuffer.current.slice(0, -1);
@@ -79,9 +82,14 @@ export default function SerialConsolePage({ onBack }: Props) {
     };
   }, []);
 
-  // Forward all incoming WS messages to the terminal
+  // Forward all incoming WS messages to the terminal, suppressing our own echoes
   useEffect(() => {
     return subscribe((msg) => {
+      const idx = echoQueue.current.indexOf(msg);
+      if (idx !== -1) {
+        echoQueue.current.splice(idx, 1);
+        return;
+      }
       termRef.current?.write(msg);
     });
   }, [subscribe]);