Improve string handling for NODE_OPTIONS and PYTHONPATH

Use filter(Boolean).join() to avoid extra spaces and properly handle
missing environment variables. This ensures clean paths even when
some variables are empty or undefined.

Co-authored-by: whyour <22700758+whyour@users.noreply.github.com>

shell/preload/sitecustomize.js

@@ -43,7 +43,7 @@ function run() {
 
     // Export NODE_OPTIONS so task_before can use it for any node commands
     const nodeOptionsForBash = file_preload_js
-      ? `-r ${file_preload_js} ${PREV_NODE_OPTIONS || ''}`
+      ? ['-r', file_preload_js, PREV_NODE_OPTIONS].filter(Boolean).join(' ')
       : PREV_NODE_OPTIONS || '';
 
     const commands = [

shell/preload/sitecustomize.py

@@ -52,7 +52,7 @@ def run():
         temp_file = f"/tmp/env_{os.getpid()}.json"
         
         # Export PYTHONPATH so task_before can use it for any python commands
-        pythonpath_for_bash = f"{dir_preload}:{dir_config}:{prev_pythonpath}" if dir_preload else prev_pythonpath
+        pythonpath_for_bash = ':'.join(filter(None, [dir_preload, dir_config, prev_pythonpath]))
         
         # 构建命令数组
         commands = [