小红书导出三条读写命令挪到阻塞线程池

- commands 新增 offload：用 tokio::task::spawn_blocking 包住同步文件 IO
- read / readHash / save 三条命令改走 offload，JoinError 收口成 ExportUnavailable

apps/ai-game-creator-shell/src-tauri/src/export/draft/xhs_minitool/commands.rs

@@ -31,7 +31,11 @@ use super::{build, script};
 pub(crate) async fn read_xhs_minitool_export(
     project_path: String,
 ) -> Result<XHSMiniToolExportState, XHSMiniToolExportReadError> {
-    let result = read_content(&project_path);
+    let result = offload({
+        let project_path = project_path.clone();
+        move || read_content(&project_path)
+    })
+    .await;
     report("read", &project_path, &result);
     result
 }
@@ -43,7 +47,11 @@ pub(crate) async fn read_xhs_minitool_export(
 pub(crate) async fn read_xhs_minitool_export_hash(
     project_path: String,
 ) -> Result<String, XHSMiniToolExportReadError> {
-    let result = read_content_hash(&project_path);
+    let result = offload({
+        let project_path = project_path.clone();
+        move || read_content_hash(&project_path)
+    })
+    .await;
     report("readHash", &project_path, &result);
     result
 }
@@ -58,7 +66,13 @@ pub(crate) async fn save_xhs_minitool_export_form(
     form: XHSMiniToolExportForm,
     base_hash: String,
 ) -> Result<String, XHSMiniToolExportSaveError> {
-    let result = save_form(&project_path, &form, &base_hash);
+    let result = offload({
+        let project_path = project_path.clone();
+        let form = form.clone();
+        let base_hash = base_hash.clone();
+        move || save_form(&project_path, &form, &base_hash)
+    })
+    .await;
     report("save", &project_path, &result);
     if let Ok(hash) = &result {
         app_log!(
@@ -109,6 +123,25 @@ fn project_root(project_path: &str) -> Result<PathBuf, ExportUnavailable> {
     Ok(root)
 }
 
+/// 把小块同步 IO 挪到 Tokio 的阻塞线程池。
+///
+/// 读命令每 2 秒被轮询一次，注册表 + `package.json` 探测虽然小，但直接在 `async fn` 里做同步
+/// 文件 IO 会占着 worker 线程，拖慢同一 runtime 上的其它异步任务（构建子进程、SpacetimeDB
+/// 客户端）。任务 panic 时 `JoinError` 收口成 `ExportUnavailable`，走各命令既有的失败表。
+async fn offload<T, E, F>(job: F) -> Result<T, E>
+where
+    T: Send + 'static,
+    E: From<ExportUnavailable> + Send + 'static,
+    F: FnOnce() -> Result<T, E> + Send + 'static,
+{
+    match tokio::task::spawn_blocking(job).await {
+        Ok(result) => result,
+        Err(error) => Err(E::from(ExportUnavailable::new(format!(
+            "后台执行导出读写任务失败：{error}"
+        )))),
+    }
+}
+
 fn read_content(project_path: &str) -> Result<XHSMiniToolExportState, XHSMiniToolExportReadError> {
     let root = project_root(project_path)?;
     Ok(content(