test(FN-000): harden local test suite

packages/droid-cli/vitest.config.ts

@@ -1,5 +1,8 @@
 import { defineConfig } from "vitest/config";
 import { resolve } from "node:path";
+import { computeMaxWorkers } from "../core/src/__test-utils__/vitest-workers";
+
+const maxWorkers = computeMaxWorkers();
 
 export default defineConfig({
   test: {
@@ -9,6 +12,10 @@ export default defineConfig({
       resolve(__dirname, "../core/src/__test-utils__/vitest-setup.ts"),
     ],
     globalSetup: [resolve(__dirname, "../core/src/__test-utils__/vitest-teardown.ts")],
+    pool: "forks",
+    maxWorkers,
+    poolOptions: { forks: { minForks: 1, maxForks: maxWorkers } },
+    fileParallelism: true,
     coverage: {
       provider: "v8",
       reporter: ["text", "json-summary"],