zstd 2

DSH session log repair: scans zstd session logs for event types the host does not know and marks them ignorable with a compliant frame rewrite (backup included). Skips archived sessions by default, caches per-file verdicts, and is read-only in scan mode.

会话成本审计：看看一次对话的 token 花在哪、哪一步贵，并把优化建议做成一键可应用的修改。