perf: fix slice boundary panics, eliminate string allocation in stdio reader, fix lua table nesting bug, and optimize nvim socket chunk size

mcp-stdio/src/lib.rs

@@ -14,7 +14,9 @@ pub async fn read_mcp_message<R: tokio::io::AsyncRead + Unpin>(
         }
 
         if line.starts_with('{') {
-            return Some(line.trim_end().to_string());
+            let len = line.trim_end().len();
+            line.truncate(len);
+            return Some(line);
         }
 
         let line = line.trim_end();