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/tests/fixtures/extension.form-schema.json

@@ -24,6 +24,12 @@
         "action": "lookup",
         "actionLabel": "Look up",
         "fill": ["name"]
+      },
+      {
+        "name": "summary",
+        "label": "Summary",
+        "type": "partial",
+        "path": "summary"
       }
     ],
     "messages": {