fix(official-sync): 清理未被引用的孤儿 staging 目录

同版本失败 staging 复用已由 060b7d7 处理，但跨版本失败、或被 trim/去重挤出
failed_versions 记录后残留的 .staging/<id> 目录永不被复用也无人清理，长期 daemon
场景下多 GB 孤儿目录会累积耗尽磁盘。

新增 gc_orphan_staging：枚举 .staging 下子目录，只保留 in_progress_version 与
failed_versions 引用的 <id>，删除其余（跳过普通文件与 symlink，staging 根不存在
时无操作）。在同步成功发布后（读取最新版本状态）和 clean-stable（后台已停止）两处
调用；GC 失败仅告警，不影响发布结果。

对应 issue #18 维护清单 1-4。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

infrastructure/src/bin/bat_official_sync.rs

@@ -1,11 +1,11 @@
 use bat_adapters::official::yostar_jp::PatchPlatform;
 use bat_infrastructure::{
-    lexical_absolute, open_append_file, read_file_no_symlink, read_version_state, redact_proxy_url,
-    resolve_curl_proxy, validate_output_root, validate_runtime_state_dir, write_file_atomic,
-    CurlProxyConfig, CurlProxyMode, OfficialFailedVersionRecord, OfficialServerInfoSource,
-    OfficialUpdateConfig, OfficialUpdateProgress, OfficialUpdateReport, OfficialUpdateService,
-    OfficialUpdateStatus, OfficialVerificationSummary, OfficialVersionRecord, OfficialVersionState,
-    PRIVATE_FILE_MODE,
+    gc_orphan_staging, lexical_absolute, open_append_file, read_file_no_symlink,
+    read_version_state, redact_proxy_url, resolve_curl_proxy, validate_output_root,
+    validate_runtime_state_dir, write_file_atomic, CurlProxyConfig, CurlProxyMode,
+    OfficialFailedVersionRecord, OfficialServerInfoSource, OfficialUpdateConfig,
+    OfficialUpdateProgress, OfficialUpdateReport, OfficialUpdateService, OfficialUpdateStatus,
+    OfficialVerificationSummary, OfficialVersionRecord, OfficialVersionState, PRIVATE_FILE_MODE,
 };
 use serde::{Deserialize, Serialize};
 use std::env;
@@ -2979,6 +2979,11 @@ fn run_clean_stable_command(options: &CliOptions) -> anyhow::Result<()> {
         removed_paths.push(proxy_secret_path);
     }
 
+    // 后台已停止，清理未被版本状态引用的孤儿 staging 目录。
+    if let Some(state) = read_version_state(&options.config.version_state_path())? {
+        removed_paths.extend(gc_orphan_staging(&options.config.output_root, &state)?);
+    }
+
     let report = CleanStableReport {
         command: "clean-stable",
         status: if skipped_paths.is_empty() {