dsh-tensorlake-sandbox: Moving DeepSeek Harness Execution into Tensorlake Sandbox

`@tensorlakeai/dsh-sandbox` is the MIT-licensed sandbox execution plugin provided by Tensorlake for DeepSeek Harness (dsh). It relocates dsh's file, subprocess, Bash, terminal, and LSP operations into ephemeral Tensorlake micro-VMs to achieve isolation from the host environment. The plugin is installed as a dsh bundle, requiring no modifications to the Harness core, and supports automatic sandbox creation upon profile startup and termination upon exit. It ensures security by validating working directory permissions, providing managed image support, and strictly isolating sensitive credentials such as API keys. Users need to have a Node.js 22.19+ environment and configure the corresponding keys, accessing the plugin via `dsh plugin install @tensorlakeai/dsh-sandbox`.