小红书导出失败日志按字符数截断

- commands.rs 的 log_failure 落盘前经 bounded_for_log 截到 512 字符，CommandFailed 的 4KB 脚本输出不再整段写进 AppData 日志与去重表

- 新增 bounded_for_log 的短文本与中文边界用例

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

@@ -151,8 +151,15 @@ fn report<T, E: std::fmt::Debug>(command: &'static str, project_path: &str, resu
     }
 }
 
+/// 一条失败日志最多记多少个字符。
+///
+/// `CommandFailed` 的 `Debug` 里带着最多 4,000 字符的脚本输出尾部，原样落进 AppData 日志会把一次
+/// 失败撑成好几 KB，去重表也跟着留一份长字符串。日志只需要认得出「哪个变体、哪条命令失败」，
+/// 完整现场已经结构化回给前端了。
+const MAX_LOGGED_FAILURE_CHARS: usize = 512;
+
 fn log_failure(command: &'static str, project_path: &str, error: &impl std::fmt::Debug) {
-    let message = format!("{error:?}");
+    let message = bounded_for_log(&format!("{error:?}"), MAX_LOGGED_FAILURE_CHARS);
     if let Ok(mut last) = LAST_FAILURE.lock() {
         if last.get(command).is_some_and(|seen| *seen == message) {
             return;
@@ -162,6 +169,15 @@ fn log_failure(command: &'static str, project_path: &str, error: &impl std::fmt:
     app_log!("export.{command}.failed project={project_path}: {message}");
 }
 
+/// 按**字符**（不是字节）截断日志文本，避免切坏 UTF-8；发生截断时补一个省略号说明。
+fn bounded_for_log(message: &str, max_chars: usize) -> String {
+    if message.chars().count() <= max_chars {
+        return message.to_string();
+    }
+    let head: String = message.chars().take(max_chars).collect();
+    format!("{head}…")
+}
+
 fn clear_failure(command: &'static str) {
     if let Ok(mut last) = LAST_FAILURE.lock() {
         last.remove(command);
@@ -176,7 +192,7 @@ fn short(hash: &str) -> &str {
 
 #[cfg(test)]
 mod tests {
-    use super::short;
+    use super::{bounded_for_log, short};
 
     #[test]
     fn short_keeps_first_eight_characters() {
@@ -184,4 +200,11 @@ mod tests {
         assert_eq!(short("0123"), "0123");
         assert_eq!(short(""), "");
     }
+
+    #[test]
+    fn bounded_for_log_keeps_short_text_and_truncates_on_char_boundaries() {
+        assert_eq!(bounded_for_log("构建失败", 8), "构建失败");
+        // 按字符截断：4 个中文字符不会被切坏，末尾补省略号。
+        assert_eq!(bounded_for_log("一二三四五六", 4), "一二三四…");
+    }
 }