dsh-session-memo: DSH Conversation Sidebar Memo Plugin

`dsh-session-memo` is a DSH Web UI plugin that provides a project context summary in the conversation sidebar. It automatically probes Git sync status, npm version differences, and project versions through a floating panel, and supports manual memo entry. The plugin uses a Host + Browser dual-end architecture, probes only when the panel is opened, and has read-only permissions. After installation, click the 📋 button in the conversation header to use it.