dsh-file-annotations: Send annotations from file preview along with the file.

The DSH client plugin maintained by DEVbyQIN enables writing text or area annotations in the right-side file preview; these annotations appear above the main input box and are sent together with the message. Annotations are isolated per session and fall on the workspace's JSON and PNG crop images. Once received by the host, they are moved to history, and drafts can be recovered in case of failure. This document verifies the functionality, storage format, installation commands, typical usage, and limitations: it does not override diff and line number anchoring, does not determine annotation expiration, relies on DSH's conversation, sessions, and inputTriggers services, and runs with the permissions of the current dsh process. Source code and the MIT license must be checked prior to installation.