feat(core-ui): add CookieConsentBanner headless component

Implements the EU-compliant cookie consent banner with:
- modal + banner variants, CNIL equal-prominence Reject/Accept buttons
- granular category toggles (essential non-toggleable)
- __consent_state cookie management (SameSite=Lax, Secure, 1-yr, _v:1)
- render-prop overrides: renderHeader, renderCategoryRow, renderActions
- useConsent() integration when ConsentProvider is present
- CookieConsentBannerLoader SSR-safe wrapper
- RTL behavioral tests: Reject All, Save Selected, ESC=Reject, focus-trap
- Storybook stories for modal, banner, render-prop, and a11y tab demo
- jsdom configured with HTTPS origin for Secure cookie testing

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-ui/src/cookie-consent-banner/cookie-consent-banner-loader.tsx

@@ -0,0 +1,26 @@
+"use client";
+
+import { useState, useEffect, type ComponentPropsWithoutRef } from "react";
+import { CookieConsentBanner } from "./cookie-consent-banner";
+
+export type CookieConsentBannerLoaderProps = ComponentPropsWithoutRef<
+  typeof CookieConsentBanner
+>;
+
+/**
+ * SSR-safe wrapper that renders null on the server and mounts
+ * <CookieConsentBanner> client-side only (after hydration).
+ */
+export function CookieConsentBannerLoader(
+  props: CookieConsentBannerLoaderProps,
+) {
+  const [mounted, setMounted] = useState(false);
+
+  useEffect(() => {
+    setMounted(true);
+  }, []);
+
+  if (!mounted) return null;
+
+  return <CookieConsentBanner {...props} />;
+}