Tensorlake sandbox plugin

Key features

• @tensorlakeai/dsh-sandbox moves DeepSeek Harness file, subprocess, Bash, terminal, and LSP operations into one short-lived Tensorlake microVM.
• A successful run reports /home/tl-user/workspace from pwd, the tl-user identity from id, and reads hello back from the file.
• It is an installable dsh bundle and does not require changes to the Harness installation.
• The model-facing working directory is the same remote Linux path, so the response should not mention or fall back from a host-machine path.