fix algo tree node name bug

src/tree.py

@@ -108,7 +108,7 @@ class TreeWalker:
                 for index, section_node in enumerate(chapter_node["children"]):
                     section_title = list(section_node.keys())[0]
                     full_path = os.path.join(
-                        chapter_path, f"{section_node['origin_num']}.{section_title}")
+                        chapter_path, f"{section_title}")
                     if os.path.isdir(full_path):
                         self.ensure_exercises(full_path)
                     else:
@@ -273,7 +273,7 @@ class TreeWalker:
         config = self.ensure_section_config(full_name)
         num, name = self.extract_node_env(full_name)
         result = {
-            name: {
+            f"{num}.{name}": {
                 "node_id": config["node_id"],
                 "keywords": config["keywords"],
                 "children": config.get("children", [])