插件

在 DSH 设置中加入原生插件商店，支持目录搜索、标签筛选、排序、安装与已安装插件管理。

DSH context-pressure guard: when a session's next request would carry a dangerously large prompt, tell the user at turn end to write the handoff and start a new session. Consumes the official token-meter contextPressure projection; injects no prompt, regi