Vertical Sortable lists now stretch children to full width by default

What changed

The default vertical layout of Sortable (from @cherrystudio/ui) switched its cross-axis alignment from items-center to items-stretch. Vertical sortable lists — used in Provider Settings v2 (provider list, model list, api-key list) and elsewhere — now render each item full-width along the container's main axis instead of hugging its intrinsic content width.

Why this matters to the user

Affected lists look slightly different in v2:

• Items that used to sit centered with whitespace on both sides now span the full row, so drag handles, kebab menus, and right-side action clusters land flush against the row edges.
• Selected / hover states cover the full row width, matching the rest of the v2 settings UI.
• Horizontal sortable lists are unchanged (still items-center).

What the user should do

Nothing — automatic. Drag-and-drop behavior is identical; only the visual width of each row changes.

Notes for release manager

Component-level change in @cherrystudio/ui (packages/ui/src/components/composites/Sortable/Sortable.tsx). External consumers that depended on the previous items-center default and want the v1 look back can wrap items in a fixed-width container or pass an explicit className override on the Sortable row. No code change is required inside the Cherry Studio app itself.