dsh-project: DeepSeek Harness Project Management Plugin

The DeepSeek Harness (DSH) plugin `dsh-project` introduces the concept of "projects" through a modular architecture, addressing the issue of fragmented resources in existing workflows. It allows users to aggregate folders, sessions, and memory instructions into a unified project tree, supporting cross-folder session management. The plugin injects project memory and instructions via `PROJECT.md` and `AGENTS.md`, and provides tools for writing to and reading from memory. While session ownership must be explicitly designated and the memory mechanism is still being refined, the plugin significantly improves the maintenance efficiency of complex Agent workflows.