fix(config): respect user's external_directory permission setting

applyToolConfig() forcibly overrode the user's external_directory
permission to 'allow' by placing OMO defaults after the user config
spread. Reorder so defaults come first and user config spreads on
top, allowing users to set 'ask' or 'deny'. The task permission
remains forced to 'deny' after the spread for security.

Closes #1973

src/plugin-handlers/tool-config-handler.ts

@@ -99,9 +99,9 @@ export function applyToolConfig(params: {
   }
 
   params.config.permission = {
-    ...(params.config.permission as Record<string, unknown>),
     webfetch: "allow",
     external_directory: "allow",
+    ...(params.config.permission as Record<string, unknown>),
     task: "deny",
   };
 }