dsh-notebook-knowledge-studio: Run a NotebookLM-style local knowledge workbench in DSH Web UI

# Introduction Intelligent agent developers typically accumulate a wealth of materials locally: documents, scraped webpages, and pasted snippets. To use them for Q&A and organization, the common approach is to upload them to an online note-taking service and rely on its AI features—the trade-off being that the data leaves your local machine. If you are already using DeepSeek Harness (dsh) and agree with its "everything is a plugin" philosophy, you can actually mount a local-first knowledge workbench directly in the Web UI. The `iZY3/dsh-notebook-knowledge-studio` introduced below is exactly such a plugin: its workflow mimics NotebookLM, and data is stored in local Markdown files.