fix(mcp): skip sync when target CLI app is not installed

Add guard functions to check if Claude/Codex/Gemini CLI has been
initialized before attempting to sync MCP configurations. This prevents
creating unwanted config files in directories that don't exist.

- Claude: check ~/.claude dir OR ~/.claude.json file exists
- Codex: check ~/.codex dir exists
- Gemini: check ~/.gemini dir exists

When the target app is not installed, sync operations now silently
succeed without writing any files, allowing users to manage MCP servers
for apps they actually use without side effects on others.

src-tauri/src/mcp/codex.rs

@@ -13,6 +13,12 @@ use crate::error::AppError;
 
 use super::validation::{extract_server_spec, validate_server_spec};
 
+fn should_sync_codex_mcp() -> bool {
+    // Codex 未安装/未初始化时：~/.codex 目录不存在。
+    // 按用户偏好：目录缺失时跳过写入/删除，不创建任何文件或目录。
+    crate::codex_config::get_codex_config_dir().exists()
+}
+
 /// 返回已启用的 MCP 服务器（过滤 enabled==true）
 fn collect_enabled_servers(cfg: &McpConfig) -> HashMap<String, Value> {
     let mut out = HashMap::new();
@@ -273,6 +279,9 @@ pub fn import_from_codex(config: &mut MultiAppConfig) -> Result<usize, AppError>
 /// - 仅更新 `mcp_servers` 表，保留其它键
 /// - 仅写入启用项；无启用项时清理 mcp_servers 表
 pub fn sync_enabled_to_codex(config: &MultiAppConfig) -> Result<(), AppError> {
+    if !should_sync_codex_mcp() {
+        return Ok(());
+    }
     use toml_edit::{Item, Table};
 
     // 1) 收集启用项（Codex 维度）
@@ -339,6 +348,9 @@ pub fn sync_single_server_to_codex(
     id: &str,
     server_spec: &Value,
 ) -> Result<(), AppError> {
+    if !should_sync_codex_mcp() {
+        return Ok(());
+    }
     use toml_edit::Item;
 
     // 读取现有的 config.toml
@@ -385,6 +397,9 @@ pub fn sync_single_server_to_codex(
 /// 从 Codex live 配置中移除单个 MCP 服务器
 /// 从正确的 [mcp_servers] 表中删除，同时清理可能存在于错误位置 [mcp.servers] 的数据
 pub fn remove_server_from_codex(id: &str) -> Result<(), AppError> {
+    if !should_sync_codex_mcp() {
+        return Ok(());
+    }
     let config_path = crate::codex_config::get_codex_config_path();
 
     if !config_path.exists() {