test: default vitest root projects to threads

test/scripts/test-extension.test.ts

@@ -146,7 +146,9 @@ describe("scripts/test-extension.mjs", () => {
         resolveExtensionTestPlan({ cwd: process.cwd(), targetArg: extensionId }).hasTests,
     );
 
-    expect(uniqueAssigned.toSorted((left, right) => left.localeCompare(right))).toEqual(expected);
+    expect(uniqueAssigned.toSorted((left, right) => left.localeCompare(right))).toEqual(
+      expected.toSorted((left, right) => left.localeCompare(right)),
+    );
     expect(assigned).toHaveLength(expected.length);
 
     const totals = shards.map((shard) => shard.testFileCount);

test/vitest-projects-config.test.ts

@@ -1,8 +1,26 @@
 import { describe, expect, it } from "vitest";
+import { createAgentsVitestConfig } from "../vitest.agents.config.ts";
+import { createCommandsVitestConfig } from "../vitest.commands.config.ts";
 import baseConfig, { rootVitestProjects } from "../vitest.config.ts";
+import { createGatewayVitestConfig } from "../vitest.gateway.config.ts";
+import { createUiVitestConfig } from "../vitest.ui.config.ts";
 
 describe("projects vitest config", () => {
   it("defines the native root project list for all non-live Vitest lanes", () => {
     expect(baseConfig.test?.projects).toEqual([...rootVitestProjects]);
   });
+
+  it("keeps hard thread exceptions on forks", () => {
+    expect(createGatewayVitestConfig().test.pool).toBe("forks");
+    expect(createAgentsVitestConfig().test.pool).toBe("forks");
+    expect(createCommandsVitestConfig().test.pool).toBe("forks");
+  });
+
+  it("keeps the root ui lane aligned with the jsdom ui project setup", () => {
+    const config = createUiVitestConfig();
+    expect(config.test.environment).toBe("jsdom");
+    expect(config.test.isolate).toBe(true);
+    expect(config.test.runner).toBeUndefined();
+    expect(config.test.setupFiles).toContain("ui/src/test-helpers/lit-warnings.setup.ts");
+  });
 });