dsh-autonomy: Switch between Chat and Agent in DSH without leaving the session

When developing with DeepSeek Harness (DSH), we often encounter two alternating requirements: at times, we want the agent to independently research, modify files, and execute commands to complete the full agent loop; at other times, we only seek a concise answer, keeping full control in our own hands. Modifying the agent preset can alter behavior, but this is a session-level replacement that is inappropriate while a session is already in progress. dsh-autonomy fills this gap by adjusting the autonomy level of the current session without replacing the session's model, preset, history, sandbox, or permission policy. The DSH ecosystem operates on the philosophy of "everything is a plugin," and this capability is integrated as a plugin. The following is an introduction.