dsh-budget-split: Budget Allocation

The `dsh-budget-split` plugin for DeepSeek Harness (DSH) is designed to support household financial planning. By registering the `budget_split` tool, it generates budget plans based on input parameters. Its key benefit is a pure Node.js implementation with no network dependencies, making it easy for developers to integrate directly. Developers can install it using the `dsh plugin add` command and use it with the DSH toolkit, providing agents with a lightweight, standalone solution for basic financial planning.