feat: initialize standalone agent-workflow

vitest.config.ts

@@ -0,0 +1,20 @@
+import { defineConfig } from "vitest/config";
+
+/**
+ * Vitest config for the agent-workflow package.
+ *
+ * - node environment (CLI unit tests, no DOM).
+ * - Tests live under src/.
+ */
+export default defineConfig({
+  test: {
+    environment: "node",
+    include: ["src/**/*.test.ts"],
+    reporters: ["default"],
+    // The signal/abort timing tests in child-process.test.ts spawn real
+    // subprocesses and are wall-clock sensitive; under parallel load the abort
+    // grace margin can slip. Retry absorbs that flakiness without forcing the
+    // whole suite to run serially (which would cost ~10s).
+    retry: 2,
+  },
+});