dsh-notebook: DSH Sidebar Notebook

The DeepSeek Harness plugin `dsh-notebook` integrates lightweight note-taking and referencing capabilities. It runs in the DSH right sidebar, supports creating notes with images, and allows you to click a title to copy it or type the `@` symbol to insert a reference. The plugin provides quick saving of selected text and archiving of full responses. Data is stored on local disk with atomic write support, but without rich text, cloud synchronization, or version history. It is suitable for developers who need to record technical details or context across sessions.