plugin-evolve: Tool Plugin Evolution Controller for DeepSeek Harness

`plugin-evolve` is a host-agnostic controller for DeepSeek Harness (DSH) that orchestrates the entire process of tool plugin evolution from signal recording to solidification. It supports in-process hot mounting, enabling validated plugins to be injected directly into the current process without a restart. It manages tool evolution via a standardized state machine encompassing signal recording, analysis, abstraction, validation, mounting, scoring, and solidification. With strict sandbox constraints to ensure security, it helps developers create dedicated tools for specific error signals, completing the experimental closed loop for DSH plugin development.