dsh-workspace-default-path: Remember the Last Directory in the Add Workspace Flow

`dsh-workspace-default-path` is a DeepSeek Harness plugin designed to simplify the process of adding a workspace. It uses a memory mechanism to automatically record the last used directory and directly navigates to that path when the user clicks “Add workspace” again. The plugin can be controlled via a toggle in Settings, supports hot reloading, and does not require a service restart, making it suitable for developers who perform frequent operations.