Group migration

Replace the removed Group compatibility API.

The deprecated Group registry entry, useGroup context, groupItemClasses helper, and Group demos have been removed in this breaking release.

• Use Button Group for attached button actions. Give the group an accessible name.
• Use Input Group for input adornments and associated actions.
• Use Field, FieldGroup, and FieldSet for related form controls and vertical layouts.
• Use ordinary flex or grid layout for unrelated presentation. Button, Input, and Select no longer infer their appearance from Group context.

import { Button } from '@/components/ui/button';import { ButtonGroup } from '@/components/ui/button-group';
<ButtonGroup aria-label="Save changes">  <Button onClick={cancel} type="button" variant="outline">    Cancel  </Button>  <Button type="submit">Save</Button></ButtonGroup>;

Reinstall the replacement and all existing reverse dependents with --overwrite, migrate calls, then remove the old copied Group directory. Do not retain an alias for the retired component.