dsh-synthetic-web-search: Synthetic Search Backend for DeepSeek Harness

The `ctx.web` module of DeepSeek Harness integrates with Synthetic Search. This plugin provides Provider registration and response field mapping capabilities. It runs as a Host-plane plugin and requires `@deepseek-ai/dsh-tool-web`. It supports configuring credentials via the UI or environment variables and maps Synthetic Search response fields to the Harness vocabulary. After installation, a restart is required for the changes to take effect, and the plugin will automatically take over the default search Provider. The plugin is compatible with specific versions of Harness and Node.js.