dsh-skill-mcp-center: Move DSH Skills and MCP management to the Settings page

## Preface If you frequently use DeepSeek Harness (`dsh`), you have likely run into operations like these: checking whether a specific skill is actually effective requires digging through the `system` / `user` / `workspace` / `runtime` directories layer by layer; temporarily disabling an MCP server requires modifying the configuration file and restarting; and verifying if an MCP server is connected or checking how many tools are currently down offers no built-in interface. DSH's philosophy is "everything is a plugin," and these interface-level needs can be resolved through plugins. The `dsh-skill-mcp-center` introduced below is a management center plugin written by Max-Null to address this. ## What is this `dsh-skill-mcp-center`