dsh-session-snapshot: Rolling Integrity Backup of DeepSeek Harness Sessions

`dsh-session-snapshot` is a session backup plugin for DeepSeek Harness, designed to prevent data loss caused by process crashes or log corruption. It automatically validates and creates integrity-checked snapshots at the end of each turn, ensuring that potential loss is limited to the current turn only. The plugin has zero runtime dependencies, supports retention policies through YAML configuration, and provides snapshot management, listing, and recovery features. As a “memory” category plugin, it significantly reduces session data risks when used alongside other protective tools.