Add Vue components and demo mounts for divider, step, chips, avatar, choices, select, textarea, pagination, loader ...

- Create GnDivider and GnStep Vue components.
- Export GnStep and GnDivider via plugin and index.
- Update GnSteps to render check icon for complete steps.
- Add Vue demo mounts to divider, stepper, select-textarea, pagination, loader, chips, avatar, choices partials.
- Convert chips and avatar partials to demo-section for screenshot capture.
- Expand screenshot section list.
- All 19 e2e tests green.

Co-Authored-By: Claude <noreply@anthropic.com>

Add Divider, Accordion, Stepper and FileAttachment components ...

- Implement CSS for divider, accordion, stepper and file-upload/attachment.
- Add browser Accordion helper and expose it on window.VMKUIKit.
- Add Vue adapters: GnAccordion, GnSteps, GnFileUpload, GnFileAttachment.
- Add demo partials and figma match pages for divider and attached-file.
- Fix Figma comparison flattening for transparent baselines (e.g. breadcrumbs, attached-file).
- Add vertical spacing to the demo index page to separate sections.

All Figma visual tests and the Vue adapter smoke build pass.