Theme Manifests Generated Block Schemas

Theme manifests can now generate block schemas for the CMS. Theme authors describe the fields a custom theme expects in the manifest, and editors get a form that matches.

An early milestone for custom themes

This is an early step in Basker's custom-theme architecture, moving away from one-off template fields and towards theme-described editing forms. It matters as the team prepares to support multiple customer sites without custom CMS work for each.

Themes that describe themselves

When a theme describes its own fields through a manifest, the CMS can generate the right admin form for any block. Theme authors write the schema once, and editors see the right fields. That removes a class of launch problems where the theme expected one field structure and the CMS presented another.