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/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "@repo/core-events",
+  "version": "0.0.1",
+  "private": true,
+  "type": "module",
+  "exports": {
+    ".": "./src/index.ts"
+  },
+  "scripts": {
+    "build": "tsc --noEmit",
+    "lint": "eslint .",
+    "typecheck": "tsc --noEmit",
+    "test": "vitest run"
+  },
+  "dependencies": {
+    "@repo/core-shared": "workspace:*",
+    "zod": "^3.23.0"
+  },
+  "peerDependencies": {
+    "payload": "^3.0.0"
+  },
+  "peerDependenciesMeta": {
+    "payload": { "optional": true }
+  },
+  "devDependencies": {
+    "@repo/core-eslint": "workspace:*",
+    "@repo/core-typescript": "workspace:*",
+    "typescript": "^5.8.0",
+    "vitest": "^3.0.0"
+  }
+}