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/models/person/fields.yaml

@@ -7,3 +7,7 @@ fields:
         label: acme.roster::lang.people.email
         type: text
         span: right
+    joined_ip:
+        label: acme.roster::lang.people.joined_ip
+        type: text
+        context: preview