Better Dsh Session Deletetool

Description

Delete a conversation from the DSH sidebar instead of only archiving it, and see the whole family it spawned — every subagent session and derived conversation, nested — before choosing which of them go with it; delete many at once from the trash icon beside the workspace search, aligned with the icons around it and visible under every dsh-claude-style search style. / 在会话菜单里真正删除对话；确认框会把整个家族（子智能体、派生对话及其下一层）按层级画出来，删之前先看得见，并可勾选连带删除哪些；工作区搜索图标左侧另有批量删除入口（兼容 dsh-claude-style 主题的搜索框样式三档，图标自动对齐相邻图标）。