dsh-better-composer: Markdown Demo and Context Enhancement for Web Composer

`dsh-better-composer` is an enhancement plugin for DSH Web Composer, designed to improve Markdown rendering and context management capabilities through public interfaces. Core features include Markdown visual enhancement, local deterministic completion, an interactive context map, and a long-paste clipboard that supports file materialization. Installation requires DSH 0.1.7-alpha.2 and Node.js 20+, and uses pnpm. The plugin leverages DSH public interfaces without taking over source code control, and provides an experimental context doctor feature along with detailed statistical data analysis, making it suitable for developers seeking a refined web interaction experience.