Feature: Collection sort order in admin sidebar

[Emlembow]

Problem

Collections in the admin sidebar are sorted alphabetically by slug (see `listCollections` in `packages/core/src/schema/registry.ts:85` — `.orderBy("slug", "asc")`). This forces arbitrary ordering that rarely matches how content should be presented on the site.

For example, a portfolio site with `positions`, `projects`, `education`, `certifications`, `endorsements`, `posts`, `pages` always shows them in alphabetical order in the admin: Certifications → Education → Endorsements → Pages → Positions → Posts → Projects — regardless of the logical order the site renders them in.

Proposed Solution

Add a `sort_order` column to `_emdash_collections` (nullable integer). Update `listCollections` to `.orderBy("sort_order", "asc")` with a secondary sort on `slug` for ties (and for collections with no explicit order).

Schema change

• Migration: `ALTER TABLE _emdash_collections ADD COLUMN sort_order INTEGER`
• Update `Collection` type and seed schema to accept `sortOrder` / `sort_order`
• Expose reordering in the admin UI (drag-to-reorder, like fields/menus/widgets already have)

Seed file

```jsonc
{
"collections": [
{ "slug": "positions", "sortOrder": 1, ... },
{ "slug": "projects", "sortOrder": 2, ... }
]
}
```

Workarounds

None that don't involve renaming slugs (which breaks URLs and queries) or forking the admin.

Related

• `packages/core/src/schema/registry.ts:85` — alphabetical sort
• `packages/admin/src/components/Sidebar.tsx:169` — consumes the manifest collections as-is
• `packages/admin/src/lib/api/schema.ts` already has `reorderFields`, `reorderMenuItems`, `reorderWidgets` — same pattern would apply for collections