fix: replace debug fmt.Println with hlog in printNode

## Problem

\printNode()\ function in \engine.go\ uses \mt.Println\ and \mt.Printf\ for debug output, which writes directly to stdout instead of using hertz's logging framework (\hlog\).

## Impact

- Debug output bypasses the logging system configuration
- Cannot control log level or output destination for these messages
- Inconsistent with the rest of the codebase which uses \hlog.SystemLogger()\

## Fix

Replace \mt.Println\/\mt.Printf\ calls with \hlog.SystemLogger().Debugf()\ to integrate with hertz's logging framework.

Local environment limitations, relying on CI/CD automated testing.

Open engine.go and locate printNode(), then inspect how nearby code uses hlog.SystemLogger(). Replace the debug fmt.Println and fmt.Printf output with Debugf logging, and verify through the project's CI/CD automated tests that the messages no longer write directly to stdout.

Written by the indexing model from the issue text.