Fix updates to always use npm registry https://registry.npmjs.org and include configured proxy in update env. Embedded runtime still uses @deepseek-ai/dsh 0.1.0-rc.7 and @zenmux/dsh-plugins 0.1.7.
- checkForUpdates: npm view now requests via --registry https://registry.npmjs.org
- downloadUpdate: npm install now requests via --registry https://registry.npmjs.org
- update env includes npm_config_* proxy settings
- checks updates and installs with Node from user runtime context as before