dsh-multi-acp: Driving DSH Sessions with an External ACP Agent CLI

This plugin turns DSH into an ACP client, driving an external CLI as the root agent instead of using DSH's built-in ACP server. It replaces the factory and registers a preset to drive external processes through DSH's engine data layer, with support for a native tool surface. Core features include sessions being taken over by an external engine, MCP servers being delivered with sessions, an engine management UI, and controllable duration and timeout. The configuration file is located at `cordis.patch.yml`; note that patches other than `insert` are applied as full replacements.