DeepSeek Harness Plugin: Fixing Repeated Retries Caused by Missing `message_stop` in Third-Party APIs

The DeepSeek Harness (DSH) plugin is designed to fix `TRANSPORT` errors and invalid retries caused by third-party gateways not sending an end signal after streamed content is complete. It listens on the `llm/stream` horizontal waterfall and intercepts errors only when the content is complete and tool-call arguments are valid JSON. It supports precise scoping via a GUI or YAML. Installation requires dsh web version >= 0.1.0-rc.6 and takes effect after a restart. It works only as a stream wrapper, does not access credentials, avoids masking genuine errors, and ensures streams are submitted normally.