ci: fix UTF-8 encoding for Chinese paths in mkdocs build

Jenkinsfile

@@ -16,8 +16,12 @@ pipeline {
 
         stage('Build Docs') {
             steps {
-                bat 'pip3 install mkdocs-material --quiet 2>nul || echo ok'
+                bat '''
-                bat 'mkdocs build --clean --site-dir site'
+                    chcp 65001 > nul
+                    set PYTHONIOENCODING=utf-8
+                    pip3 install mkdocs-material --quiet 2>nul || echo ok
+                    mkdocs build --clean --site-dir site
+                '''
             }
         }