dsh-readwrite-hub: DeepSeek Harness Read-Write Hub Plugin

`dsh-readwrite-hub` is a read-write hub plugin for DeepSeek Harness, designed to address flow-state interruptions caused by switching between file management, writing, and reading. It integrates file management, writing, and reading capabilities, supporting one-click mode switching. Core features include: a reading mode that optimizes the long-form reading experience with character-based pagination, automatic progress saving, and chapter navigation; a writing mode featuring ruled lines, layout control, and auto-save; and a library system that manages reading records, supports read-only EPUB rendering, and enforces security boundary controls. The plugin runs entirely locally and requires an application restart to take effect.