Integrate whynot-design into Economic Observatory UI

Vendor whynot-design Layer 1 (tokens, CSS) and Layer 2 (<wn-*>
components) via scripts/sync-whynot-design.sh with a pinned ref.
Migrate the observatory shell to canonical web components, keep
observatory-specific layout in styles.css, and add vendor integrity
tests plus correct JS MIME types on the dev server.

projects/coulomb-pricing/ui/vendor/whynot-design/index.js

@@ -0,0 +1,35 @@
+/* =============================================================
+ * @whynot/design — entry point
+ * ------------------------------------------------------------
+ * Side-effect import that registers every <wn-*> custom element.
+ *
+ *   import "@whynot/design";
+ *
+ * If you only need a subset, import the per-group files instead:
+ *
+ *   import "@whynot/design/atoms";
+ *   import "@whynot/design/form";
+ *   import "@whynot/design/layout";
+ *   import "@whynot/design/chrome";
+ *
+ * CSS is imported separately:
+ *
+ *   import "@whynot/design/styles/colors_and_type.css";
+ *   import "@whynot/design/styles/components.css";
+ * ============================================================= */
+
+import { defineAtoms }  from "./elements/atoms.js";
+import { defineForm }   from "./elements/form.js";
+import { defineLayout } from "./elements/layout.js";
+import { defineChrome } from "./elements/chrome.js";
+
+defineAtoms();
+defineForm();
+defineLayout();
+defineChrome();
+
+// Re-export classes for consumers that want to extend or reference them.
+export * from "./elements/atoms.js";
+export * from "./elements/form.js";
+export * from "./elements/layout.js";
+export * from "./elements/chrome.js";