dsh-unified-market: Unified Plugin Marketplace (Three-Source Aggregation, EAC Specialization)

The DSH Harness (DSH) plugin integration tool `dsh-unified-market` addresses the fragmentation of existing plugin markets and EAC Profile compatibility issues. It aggregates curated catalogs, GitHub, and npm sources, providing a one-stop solution for installation, updates, feature package management, and Profile synchronization. It supports security pre-checks, hot mounting without restarts, conflict detection, and local development linking, aiming to deliver a more stable and controllable plugin management experience for DSH Desktop.