dsh-ai-teacher: Dedicated Teaching Agent Preset for DeepSeek Harness

The `dsh-ai-teacher` plugin provided by hatter123 adds an agent preset named “AI Teacher” to DeepSeek Harness. This preset objectively explains complex concepts in a step-by-step manner based on PDF documents, supporting Socratic guidance and an invisible motivation mechanism. Users only need to run the installation command to use the plugin in DSH for in-depth learning, without cumbersome prompt engineering.