dsh-workbuddy-websearch: Integrating WorkBuddy Cloud Search

The WebSearch plugin for DeepSeek Harness (DSH) reuses the logged-in session and cloud search capabilities of the WorkBuddy desktop client to provide DSH with zero-configuration online search. It supports returning summaries with cited sources, has no hard dependencies, and is ready to use after installation and a restart, without the need to apply for an API key. It is primarily intended for Windows and macOS developers, but supports only `web_search`, not `web_fetch`, and is subject to platform restrictions.