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/styles/main.css

@@ -207,6 +207,72 @@
     opacity: 0;
     scale: 0.98;
   }
+
+  /* Partial style kit (Phase 10.1, UI-SPEC): stable class names a plugin's
+     partial templates may use, so server-rendered content looks native
+     without plugin CSS. They read only the public --c-* variables. */
+  .summer-partial {
+    font-size: 14px;
+    line-height: 1.5;
+    color: var(--c-text);
+    overflow-wrap: anywhere;
+  }
+
+  .summer-partial :where(p, ul, ol) {
+    margin: 0 0 8px;
+  }
+
+  .summer-partial :where(p, ul, ol):last-child {
+    margin-bottom: 0;
+  }
+
+  .summer-partial a {
+    color: var(--c-text);
+    text-decoration: underline;
+  }
+
+  .summer-partial a:focus-visible {
+    outline: 3px solid var(--c-ring);
+    outline-offset: 2px;
+  }
+
+  .summer-stats {
+    display: flex;
+    flex-wrap: wrap;
+    column-gap: 32px;
+    row-gap: 8px;
+    margin: 0;
+    padding: 16px 20px;
+    background: var(--c-surface);
+    border: 1px solid var(--c-border);
+    border-radius: 16px;
+    box-shadow: var(--c-shadow-card);
+  }
+
+  .summer-stat {
+    display: flex;
+    flex-direction: column-reverse;
+    gap: 4px;
+    min-width: 0;
+  }
+
+  .summer-stat__label {
+    margin: 0;
+    font-size: 13px;
+    line-height: 1.5;
+    font-weight: 400;
+    color: var(--c-muted);
+    overflow-wrap: anywhere;
+  }
+
+  .summer-stat__value {
+    margin: 0;
+    font-size: 20px;
+    line-height: 1.2;
+    font-weight: 600;
+    color: var(--c-text);
+    font-variant-numeric: tabular-nums;
+  }
 }
 
 @media (prefers-reduced-motion: reduce) {