feat(core-analytics): add React provider and useAnalytics hook

Adds a ./react subpath export to @repo/core-analytics containing
<AnalyticsProvider value={IAnalytics}> and useAnalytics(): IAnalytics.
useAnalytics() throws AnalyticsContextError when called outside a provider.
React Testing Library test verifies track() flows through context using
RecordingAnalytics. Switches vitest config to pick up .tsx test files
via environmentMatchGlobs and extends tsconfig to react-library.json
for JSX support.

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

packages/core-analytics/src/react/analytics-provider.tsx

@@ -0,0 +1,33 @@
+import { createContext, useContext, type ReactNode } from "react";
+import type { IAnalytics } from "../analytics.interface";
+
+const AnalyticsContext = createContext<IAnalytics | null>(null);
+
+export class AnalyticsContextError extends Error {
+  constructor() {
+    super("useAnalytics() must be called within an <AnalyticsProvider>.");
+    this.name = "AnalyticsContextError";
+  }
+}
+
+export function AnalyticsProvider({
+  value,
+  children,
+}: {
+  value: IAnalytics;
+  children: ReactNode;
+}) {
+  return (
+    <AnalyticsContext.Provider value={value}>
+      {children}
+    </AnalyticsContext.Provider>
+  );
+}
+
+export function useAnalytics(): IAnalytics {
+  const analytics = useContext(AnalyticsContext);
+  if (analytics === null) {
+    throw new AnalyticsContextError();
+  }
+  return analytics;
+}