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/boardwalk/dist/index.html

@@ -6,8 +6,8 @@
     <meta name="robots" content="noindex, nofollow" />
     <meta name="summer-admin-base" content="__SUMMER_ADMIN_BASE__" />
     <title>SummerCMS</title>
-    <script type="module" crossorigin src="./assets/index-8CEYdgqp.js"></script>
-    <link rel="stylesheet" crossorigin href="./assets/index-BxJxH4xB.css">
+    <script type="module" crossorigin src="./assets/index-DEJgWNHv.js"></script>
+    <link rel="stylesheet" crossorigin href="./assets/index-57SuA8gQ.css">
   </head>
   <body>
     <div id="app"></div>