dsh-essential-tools: DeepSeek Harness Engineering Plugin

The DeepSeek Harness plugin `dsh-essential-tools` (DET) is designed to turn DSH into an engineering-powered console. Key capabilities include permission-based web read/write control through a browser extension, conversation branch and message micro-version management using a Virtual Dialogue Tree (VTD), and engineering tools such as project execution, file trees, and code snapshots. The plugin also provides a global plugin manager with hot-swapping and safe rewriting, along with Cross-Dialogue Memory (CDM) and auditing. It supports zero-configuration operation, subject to browser dependencies and permission-level requirements.