修复: UX扩展审查P0批(后端git/路径确定性bug + 前端UI + 编译阻断)

后端(src-tauri):

- project.rs: 4处空if目录校验补return Err(import/relocate/scan_directory/scan_project_with_ai),目录不存在不再静默放行

- ai/tools/git.rs: exec_git改返(String,bool)治git_commit·git_branch create/switch假成功 + git_merge补失败分支 + 加CREATE_NO_WINDOW

- module.rs: run_git_cmd加CREATE_NO_WINDOW,治Windows cmd黑窗闪烁(原问题9)

前端:

- DependencyGraph.vue: 环检测高亮注入renderGraph,原被fromJSON重建抹除致功能失效

- FileExplorer.vue: 工程下拉closeDropdown加closest判定,原打不开

附(预存编译阻断顺带修):

- df-nodes ai_node_helpers.rs: extract_first_json_object临时值借用悬垂E0716

- MessageList.vue: 删isLastUser死代码(vue-tsc TS6133)

审查产出: docs/05-代码审查/UIUX扩展审查-2026-08-02.md(80条发现,8高grep核验全属实)+ docs/todo.md批次段

src-tauri/src/commands/project.rs

@@ -248,6 +248,7 @@ pub async fn import_project(
         return Err("导入路径不能为空".to_string());
     }
     if !Path::new(&path).is_dir() {
+        return Err(format!("目录不存在: {}", path));
     }
 
     // 解析 name/desc/stack(入参优先,缺省时从目录探测/读 README)。
@@ -408,6 +409,7 @@ pub async fn relocate_project_path(
     new_path: String,
 ) -> Result<ProjectRecord, String> {
     if !Path::new(&new_path).is_dir() {
+        return Err(format!("目录不存在: {}", new_path));
     }
     if let Some(conflict) = find_binding_conflict(&state, &new_path, Some(&id)).await? {
         return Err(format!("目录已被项目「{}」绑定", conflict.name));
@@ -471,6 +473,7 @@ pub async fn scan_directory_for_projects(
 ) -> Result<Vec<ScannedProjectItem>, String> {
     let root = Path::new(&root_path);
     if !root.is_dir() {
+        return Err(format!("目录不存在: {}", root_path));
     }
 
     // 1. 规则发现(spawn_blocking 防 IO 阻塞 tokio runtime)
@@ -706,6 +709,7 @@ pub async fn scan_project_with_ai(
 ) -> Result<AiScanResult, String> {
     let root = Path::new(&path);
     if !root.is_dir() {
+        return Err(format!("目录不存在: {}", path));
     }
 
     // 1. 规则探测(兜底)+ 采样(纯 IO 轻量,spawn_blocking 防 IO 阻塞 tokio runtime)