FRE-366: Add dedicated permissions page with toggle controls

- Add page slot with /permissions route for dedicated permissions management
- Add ui.page.register capability
- Create PermissionsPage component with agent list and permission toggles
- Each agent can be selected to view and toggle their permissions
- Maintains existing sidebar and detail tab functionality

Co-Authored-By: Paperclip <noreply@paperclip.ing>

plugin-agent-permissions/src/ui/index.tsx

@@ -1,2 +1,3 @@
 export { AgentPermissionsTab } from './AgentPermissionsTab';
 export { PermissionsNav } from './PermissionsNav';
+export { PermissionsPage } from './PermissionsPage';