dsh-skill-manager: DeepSeek Harness Skill Management Plugin

dsh-skill-manager is a Skill management plugin for DeepSeek Harness, designed to centrally manage the visibility and loading strategies of Skills. Core features include: selecting Skills to load for a session via the interface before starting a new conversation; globally enabling or disabling any Skill in settings (when disabled, they are hidden from the session directory and tools without deleting files); configuring the default Skill set for new conversations per workspace (fully available or a specified list); adjusting the current session's Skill configuration in real-time via a header button during a conversation; and permanently deleting user-created Skills (limited to the `~/.dsh/skills` and `~/.agents/skills` paths; project-level or built-in Skills are not supported). The plugin supports loading from SKILL.md