dsh-at-handoff: Focus on context, turn this round into a handoff document.

`dsh-at-handoff` is a context handoff plugin for DSH, maintained by Xiacqi1, and categorized under workflows. It reads context values derived from the host's `tokenMeter` and displays a capsule above the input box according to the default 120k smart line and 30k step rules. After crossing the threshold, it turns amber and provides a button. Clicking "Go to Handoff" fills the instruction as a draft into the input box for the user to send by pressing Enter. The model invokes the built-in at-handoff technique to replace this turn with a handoff document written to `<Project>/.scratch/handoff/`. The button then changes to "Go to New Session". Clicking it opens a new session in the same project and uses the document as an unsent opening message. The document is named with the last 8 digits of the session ID and a sequence number; repeated clicks do not overwrite, and old documents are archived. The plugin is configured via environment variables for thresholds, steps, and hysteresis, exposing three host interfaces: `state`, `take`, and `consume`. It has been released as `dsh-at-handoff@0.1.0`. It can be installed via the marketplace panel, `dsh plugin --profile web add`, or the desktop plugin management page, but the host must be restarted after installation. Known issues include a potential white screen and lack of console access in the desktop client during errors, and `composer.bar` is not an available slot. The content is organized based on the README and package.json.