dsh-write-create-only: Prevent write from Overwriting Existing Files

This plugin enforces a mandatory “write create-only” constraint in DeepSeek Harness (DSH), preventing the model from accidentally overwriting existing files. Core features include: intercepting only the `write` tool; denying the operation and recommending the use of `edit` if the target file already exists; allowing it if the file does not exist; and applying a conservative allow policy in uncertain cases such as invalid paths. The plugin registers a `tools/pre-execute` listener to detect file status before tool execution and perform dynamic rejection. It is mounted automatically after installation and is provided under the MIT open-source license.