dsh-file-confirm: File Modification Confirmation Mechanism

The DSH plugin `dsh-file-confirm` intercepts file write operations such as `write` and `edit` to provide diff previews and a manual confirmation mechanism in the input area. Users can choose to approve or reject the operation; rejecting it causes the tool call to fail. The plugin supports viewing long text and regex-based path filtering, without affecting read operations. It leverages official extension points to achieve a zero-intrusion design, providing DSH with a secure and simple file review capability.