dsh-msg-resize: Turn the DSH dialog area into a draggable, resizable free-floating window.

By default, DSH's chat area is centered with a fixed width. `dsh-msg-resize` (buddha68, MIT, v2.6.0) packages the message area and input box into a floating window: drag the bottom-right handle to resize (minimum 460×320), drag the top-right handle to move, double-click to reset, use the keyboard for fine-tuning, and save the position and size to `localStorage`. The floating window is constrained within the chat pane, the input box width follows the panel, and it automatically hides on narrow screens. It can be installed via the `dsh plugin add` command, or by downloading the Release archive, placing it in the profile's `node_modules`, and appending the `msg-resize insert` block to the end of `cordis.patch.yml`. Verified on DSH web 0.2.x; the plugin will silently fail if the host significantly changes the chat area structure. The panel is limited to `position: fixed` and conflicts with `dsh-chat-drag` at the handle position on the chat page.