chore(core-events): scaffold package

Create @repo/core-events package skeleton with package.json, tsconfig.json,
vitest.config.ts (using mergeConfig with nodeVitestConfig), eslint.config.js,
turbo.json (tagged core), and AGENTS.md. Register workspace via pnpm install.

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

packages/core-events/eslint.config.js

@@ -0,0 +1,3 @@
+import baseConfig from "@repo/core-eslint/base";
+
+export default baseConfig;