perf: eliminate loop string allocations and proxy mem spikes

nvim-core/src/lib.rs

@@ -37,9 +37,9 @@ pub async fn send_response(response: JsonRpcResponse) {
     // The MCP StdioTransport MUST use Newline-Delimited JSON (NDJSON).
     // Do NOT use LSP-style HTTP headers (e.g. Content-Length).
     // See MCP protocol spec (SEP-2575) and mcp-go-sdk bufio.Scanner implementation.
-    let payload = format!("{}\n", msg);
     let mut stdout = tokio::io::stdout();
-    let _ = stdout.write_all(payload.as_bytes()).await;
+    let _ = stdout.write_all(msg.as_bytes()).await;
+    let _ = stdout.write_all(b"\n").await;
     let _ = stdout.flush().await;
 }