fix: resolve CI linting failures and test path

errorfix/plugins/loader.py

@@ -1,5 +1,4 @@
-import sys
+from typing import List, Optional
-from typing import List, Optional, Dict, Any
 
 from .plugin import Plugin, PluginRegistry
 
@@ -38,7 +37,7 @@ class PluginLoader:
 
         plugin = module.register()
         if not isinstance(plugin, Plugin):
-            raise ValueError(f"register() must return a Plugin instance")
+            raise ValueError("register() must return a Plugin instance")
 
         self.registry.register(plugin)
         return plugin