dsh-session-sight: DeepSeek Harness Session Archiving and Deletion Preview Plugin

`dsh-session-sight` is a local session management plugin for DeepSeek Harness (DSH), designed to address data loss caused by accidental operations. It provides a zero-dependency solution that does not intrude into official code, supporting read-only session preview, archiving, and complete deletion from both the sidebar and the command line. Core features include sidebar session list management, Markdown-formatted message previews (the most recent 20 messages), and a safe file recycling mechanism. Through commands such as `/archive-session`, `/archived`, `/unarchive`, and `/recycle-session`, the plugin helps users review content before taking action and clearly distinguishes between “archiving (hiding)” and “deletion (recycle bin).”