dsh-plugin-agent-budget: Shared Token Budget Management for the DeepSeek Harness Agent Tree

`dsh-plugin-agent-budget` is an open-source plugin for DeepSeek Harness that manages token budgets for agent trees. It treats the entire tree or each session as a budget account, supporting tree- or session-level scope management, isolated storage, and model-aware quota control. The plugin provides degradation strategies (such as stress prompts and concurrency limits) and a local API to prevent token consumption from getting out of control. It is currently in an experimental stage, so care should be taken with dependency installation/configuration and concurrency race conditions.