refactor: improve code quality and fix linting issues

- Derive Default trait instead of manual implementation for McpRoot and ProviderManager
- Remove redundant closures in codex_config.rs and config.rs
- Simplify match statements to if let patterns in migration.rs and lib.rs
- Remove unnecessary type conversions and borrows in lib.rs
- Fix i18n key inconsistency: sequentialThinking → sequential-thinking
- Format TypeScript files to match Prettier style

All clippy warnings resolved, code passes all quality checks.

src-tauri/src/config.rs

@@ -106,7 +106,7 @@ pub fn sanitize_provider_name(name: &str) -> String {
 /// 获取供应商配置文件路径
 pub fn get_provider_config_path(provider_id: &str, provider_name: Option<&str>) -> PathBuf {
     let base_name = provider_name
-        .map(|name| sanitize_provider_name(name))
+        .map(sanitize_provider_name)
         .unwrap_or_else(|| sanitize_provider_name(provider_id));
 
     get_claude_config_dir().join(format!("settings-{}.json", base_name))