dsh-session-chat-share: Share Conversation Messages in DSH as Markdown, HTML, TXT, or PNG

This is a DeepSeek Harness community plugin that allows users to export conversation content locally. It supports exporting to Markdown, HTML, TXT, or PNG via the `/share` command and a menu entry, with optional inclusion of tool calls or sub-agent conversations. The plugin redacts sensitive information, supports custom message ranges, and does not upload data to a server.