refactor: remove sandbox system and simplify agent architecture

Remove the entire sandbox security system including:
- All sandbox-related Rust code and dependencies (gaol crate)
- Sandbox command handlers and platform-specific implementations
- Comprehensive test suite for sandbox functionality
- Agent sandbox settings UI components

Simplify agent configuration by removing sandbox and permission fields:
- Remove sandbox_enabled, enable_file_read, enable_file_write, enable_network from agent configs
- Update all CC agents to use simplified configuration format
- Remove sandbox references from documentation and UI

src/components/TimelineNavigator.tsx

@@ -580,4 +580,4 @@ export const TimelineNavigator: React.FC<TimelineNavigatorProps> = ({
       </Dialog>
     </div>
   );
-}; 
+};