fix: address code review issues for Access support

- Fix import_vba_access() to actually save database via DoCmd.Save()
- Update stale module docstring in extract_vba.py
- Validate file extensions in get_file_type() instead of silently
  defaulting to excel
- Scan both Excel/ and Access/ directories in interactive mode

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

import_vba.py

@@ -50,11 +50,16 @@ def get_file_type(file_path: Path) -> str:
 
     Returns:
         'access' 或 'excel'
+
+    Raises:
+        ValueError: 不支持的文件扩展名
     """
     ext = file_path.suffix.lower()
     if ext in ACCESS_EXTENSIONS:
         return 'access'
-    return 'excel'
+    if ext in EXCEL_EXTENSIONS:
+        return 'excel'
+    raise ValueError(f"不支持的文件类型: {ext}（支持: .xlsm, .xls, .xlsb, .accdb, .mdb）")
 
 
 class VBAImporter:
@@ -411,8 +416,7 @@ class VBAImporter:
 
             print("\n正在保存...")
             try:
-                import time
-                time.sleep(1)  # 等待 VBE 完成
+                access.DoCmd.Save()
                 print("已保存更改。")
             except Exception as e:
                 print(f"保存时出错: {e}")