Add AnalyticsLoader component with idle-callback initialization

src/observability/analytics/loader.tsx

@@ -0,0 +1,52 @@
+"use client";
+
+import { useEffect, useRef, useState } from "react";
+import type { ReactNode } from "react";
+import type { Analytics, AnalyticsProviders } from "./types.js";
+import type { Logger } from "@/observability/logger/types";
+import { createAnalytics } from "./facade.js";
+import { AnalyticsContext } from "./provider.js";
+
+export interface AnalyticsLoaderProps {
+  enabled: AnalyticsProviders;
+  consent: { analytics: boolean; telemetry: boolean };
+  logger: Logger;
+  children: ReactNode;
+}
+
+/**
+ * Mounts in the root layout. Waits for idle callback, then initializes
+ * analytics adapters and provides the Analytics instance to the tree.
+ */
+export function AnalyticsLoader({
+  enabled,
+  consent,
+  logger,
+  children,
+}: AnalyticsLoaderProps): JSX.Element {
+  const [analytics, setAnalytics] = useState<Analytics | null>(null);
+  const initRef = useRef(false);
+
+  useEffect(() => {
+    if (initRef.current) return;
+    initRef.current = true;
+
+    const init = () => {
+      const instance = createAnalytics({ enabled, consent, logger });
+      setAnalytics(instance);
+    };
+
+    if (typeof window !== "undefined" && "requestIdleCallback" in window) {
+      (window as unknown as { requestIdleCallback: (cb: () => void) => void }).requestIdleCallback(init);
+    } else {
+      // Fallback for environments without requestIdleCallback
+      setTimeout(init, 1);
+    }
+  }, [enabled, consent, logger]);
+
+  return (
+    <AnalyticsContext.Provider value={analytics}>
+      {children}
+    </AnalyticsContext.Provider>
+  );
+}