fix(tool-config): stop overriding external_directory permission

Remove the hardcoded external_directory: "allow" default from
applyToolConfig(). This was silently overriding OpenCode's built-in
default of "ask" and any user-configured external_directory permission.

With this change, external_directory permission is fully controlled by
OpenCode's defaults and user configuration, as intended.

Fixes #1973
Fixes #2194

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

@@ -100,7 +100,6 @@ export function applyToolConfig(params: {
 
   params.config.permission = {
     webfetch: "allow",
-    external_directory: "allow",
     ...(params.config.permission as Record<string, unknown>),
     task: "deny",
   };