TLEWA/dsh-if

Adds an /if slash command to DSH: the first line is a condition and the remaining lines are an instruction. A fork subagent that inherits the session tools, system prompt and message history judges the condition and answers YES or NO, and only on YES is the instruction sent to the main agent as an ordinary user message, while a NO sends nothing. The condition, judge prompt and verdict never enter the main transcript. While the agent is busy the command queues with ordinary messages, editable, removable and steerable from the queue panel, and a setting switches to the 0.2.x background mode. The judge runs read-only, and falls back to a one-shot model call over a plain transcript when the host has no context-inheriting fork provider. Supports DSH 0.2.1-rc.5 and later (verified on 0.2.1-rc.5 and 0.2.2-rc.1) and Node.js 20.3 or later.