dsh-session-scope: DeepSeek Harness Session-Level Workspace Isolation Plugin

`dsh-session-scope` is a security plugin for DeepSeek Harness (DSH), designed to limit an Agent's workspace access scope and prevent permission overreach and accidental operations. Its core principle is to separate permissions (operational capabilities) from scope (visible directories), providing `full`, `focused`, and `isolated` session scope states. The state can be switched dynamically via the `/scope` command, and, combined with filesystem projection and process isolation mechanisms on Linux, it keeps the Session's original workspace unchanged while exposing only selected directories to the Agent or enforcing strong isolation. This plugin is suitable for scenarios requiring fine-grained control over an Agent's working directory and protection against access to sensitive configurations. The project has been archived and migrated to `xarleyn/ds`