dsh-workspace-default-dir: Set the default initial directory for the DSH workspace directory selector

`dsh-workspace-default-dir` is a DSH client plugin developed and maintained by dragan2023 (MIT License), designed to address the frequent manual navigation issues faced by Windows users when the workspace directory is not the home directory. By modifying the native Windows dialog and file picker backends, this plugin allows users to customize the default initial path of the "Add Workspace" directory picker. Core features include: providing a `Settings → Workspace default directory` GUI settings card; supporting CLI commands (set/get/clear/status) for configuration; and synchronizing writes to the `DSH_PICKER_INITIAL_DIR` environment variable between the GUI and CLI.