feat: add config directory override support for WSL

- Add persistent app settings with custom Claude Code and Codex config directories
- Add config directory override UI in settings modal with manual input, browse, and reset options
- Integrate tauri-plugin-dialog for native directory picker
- Support WSL and other special environments where config paths need manual specification

Changes:
- settings.rs: Implement settings load/save and directory override logic
- SettingsModal: Add config directory override UI components
- API: Add get_config_dir and pick_directory commands

src-tauri/Cargo.toml

@@ -26,6 +26,7 @@ tauri-plugin-log = "2"
 tauri-plugin-opener = "2"
 tauri-plugin-process = "2"
 tauri-plugin-updater = "2"
+tauri-plugin-dialog = "2"
 dirs = "5.0"
 toml = "0.8"