dsh-apply-patch: Inject a Codex-style apply_patch tool into the DSH model

This plugin injects the `apply_patch` tool into DSH models, resolving errors caused by the missing tool for GPT-series models in the DSH environment. It is fully compatible with OpenAI Codex's patch format, and all file writes are executed through DSH's native sandboxing system to ensure safety. It supports model-conditional injection (GPT models only by default) and provides a real-time configuration toggle. After installation, the model can directly invoke this tool to update, add, or delete files.