feat(10.1-02): render header and form partials through an allowlisted node renderer

- partialNodes rebuilds the server node tree with h() under the server's tag, attribute and URL lists
- PartialHost owns the skeleton, empty and failure states and keeps nodes visible on refetch
- type: partial is a valueless group-labelled field rendered on create and update
- ListView shows headerPartial above the list card and refetches it after bulk delete
- summer-partial and summer-stats style kit in main.css, documented in the cabana README; dist rebuilt

admin/src/components/form/fields/WidgetField.vue

@@ -162,7 +162,7 @@ onBeforeUnmount(() => {
     :id="controlId"
     role="group"
     data-widget-host
-    :aria-labelledby="`${controlId}-label`"
+    :aria-labelledby="field.label ? `${controlId}-label` : undefined"
     :aria-describedby="describedBy || undefined"
     :aria-busy="status === 'loading' ? 'true' : undefined"
     class="flex min-h-input items-center"