dsh-book-reader: DSH Reading Workbench Plugin (Phase 1 MVP)

The dsh-book-reader plugin for DeepSeek Harness (DSH) aims to resolve the disconnect between local PDF reading and conversation flow. Built on `dsh-better-sidebar`, it provides an embedded PDF reader supporting pagination, zooming, text highlighting, and annotations, with all data stored locally and persisted. A core feature allows selected text to be sent directly to the conversation, automatically including the file path and page reference. Installation requires running a command in the DSH Desktop environment; after installation, the application must be fully restarted to load the routes. The plugin is in the MVP stage and is licensed under the MIT License.