dsh-itinerary: Itinerary Orchestration

The DSH plugin `dsh-itinerary` provides local itinerary orchestration capabilities and is maintained by uckkk. Implemented entirely in Node.js, it has no runtime network dependencies and allows developers to generate travel planning solutions directly on their local machines. The dependencies `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools` must be installed first. No additional configuration is required after installation; simply invoke the tool within a DSH session to use it.