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

admin/tests/smoke/actions.smoke.test.ts

@@ -489,7 +489,7 @@ describe('row state (UI-SPEC S4, D-12)', () => {
     expect(row.find('[data-row-state]').exists()).toBe(false)
     const link = firstCell(wrapper, 0).find('a')
     expect(link.classes()).toEqual(expect.arrayContaining(['text-text', 'no-underline']))
-    expect(link.attributes('href')).toBe('/acme/roster/people/1')
+    expect(link.attributes('href')).toBe('/acme/roster/people/1/preview')
     expect(firstCell(wrapper, 0).classes()).not.toContain('text-muted')
   })
 
@@ -507,7 +507,7 @@ describe('row state (UI-SPEC S4, D-12)', () => {
     const link = cell.find('a')
     expect(link.classes()).toEqual(expect.arrayContaining(['line-through', 'text-danger', 'min-w-0', 'truncate']))
     expect(link.find('[data-row-state]').exists()).toBe(false)
-    expect(link.attributes('href')).toBe('/acme/roster/people/2')
+    expect(link.attributes('href')).toBe('/acme/roster/people/2/preview')
     expect(cell.classes()).toEqual(expect.arrayContaining(['font-semibold', 'text-muted']))
     expect(row.findAll('td:not([data-select])')[1]!.classes()).toContain('text-muted')
     const deleted = cell.find('[data-row-state="deleted"]')