feat(12.1-02): read-only preview screen with a status hint and record actions

- config_form.yaml preview block (optional headerPartial), reported in the form schema as preview
- fields with context: preview show only on the preview screen and are never written
- form messages preview and edit; recordActions without a preview block stops boot
- SPA route {id}/preview, PreviewView and PreviewField, record actions in the footer
- mapWinterUrl maps preview/:id; the update form returns to the preview
- summer-callout partial style classes for status hints
- README, docs, OpenAPI document, TS types and the embedded build updated

modules/cabana/testdata/roster/controllers/people/config_form.yaml

@@ -3,9 +3,14 @@ form: ~/plugins/acme/roster/models/person/fields.yaml
 modelClass: Person
 defaultRedirect: acme/roster/people
 create:
-    redirect: acme/roster/people/update/:id
+    redirect: acme/roster/people/preview/:id
     redirectClose: acme/roster/people
 update:
     redirect: acme/roster/people
-    redirectClose: acme/roster/people
+    redirectClose: acme/roster/people/preview/:id
+preview:
+    headerPartial: status
 recordActions: [activate, reinstate]
+messages:
+    preview: acme.roster::lang.people.preview
+    edit: acme.roster::lang.people.edit