dsh-profile-sync: Plugin Migration Tool

`dsh-profile-sync` is a tool for safely migrating plugins between different DeepSeek Harness profiles, designed to reduce errors in manual configuration. It computes diffs, runs prechecks, and generates execution scripts to automatically compare and synchronize plugin lists. Plugins are installed via the official channel, with strict prechecks (such as path validation, entry-ID conflict detection, and declaration integrity checks) to prevent startup failures. The tool supports both CLI and panel interactions, allowing users to either generate a plan or apply changes directly. It also intelligently handles special cases such as version downgrades and differing pinning methods, ensuring accurate configuration application.