dsh-cache-stabilizer: Stabilize DeepSeek Harness cache prefix

`dsh-cache-stabilizer` is an MIT-licensed plugin for DeepSeek Harness (DSH) designed to stabilize system prompt prefixes to improve the reuse rate of Provider-side Prompt Cache. Its core functions include: first, moving the working directory (cwd) from the system prompt to the runtime-context snapshot in DSH standard or headless coding personas, ensuring that different projects share the same prefix while retaining the correct cwd; and second, normalizing the object-key order of tool schemas to facilitate prefix stabilization. This plugin does not create a new cache layer or alter the Provider's caching strategy. Additionally, it provides `