allow deepseek harness to use

Key features

• dsh-vscode-theme adds a VS Code theme importer to DeepSeek Harness Web.
• Restart the DSH Web profile after installing or rebuilding this package, then open Settings -> Plugins -> VS Code Themes.
• Ask the agent to inspect a VSIX, or call the registered tool directly
• In Settings -> Plugins -> VS Code Themes, drag in a .vsix file, select one of the theme variants it contains, and the DSH interface switches immediately.
• Parsing happens in the browser