dsh-preset-doctor: DeepSeek Harness Preset Doctor

`dsh-preset-doctor` is a plugin for DeepSeek Harness designed to resolve Agent preset loading failures caused by package name changes and configuration migration after upgrades. It supports automatic scanning, format migration, package name replacement, configuration key splitting, and path rewriting. With zero LLM involvement, it safely repairs `cordis.patch.yml` and legacy directories using backup and atomic write mechanisms. After installation, the process must be restarted, and the repair can be executed automatically via a command or in scan-only mode.