dsh-project-context

把 DSH 工作区文件夹变成项目：新会话自动注入精简的「项目工作区约定」上下文（先读代码、空目录即新建项目）；输入框旁每会话「项目」开关可将会话显式降级为普通工作区（状态渲染式注入，关时有提示，不整块消失），状态存于会话日志。

Turns each DSH workspace into a project: every new session auto-injects a project-workspace convention (read code before acting, empty folder means a brand-new project); a per-session Project toggle in the composer downgrades the session to a plain workspace with an explicit notice, with the state kept in the session log.