test(core): add PageAgentCore lifecycle tests

packages/llms/vitest.config.js

@@ -0,0 +1,10 @@
+import { defineConfig } from 'vitest/config'
+
+export default defineConfig({
+	test: {
+		name: 'llms',
+		include: ['src/**/*.test.ts'],
+		// Suppress console output from passing tests; failed tests still get their logs.
+		silent: 'passed-only',
+	},
+})