feat(FN-4621): complete Step 3 — add worktrunk resolver and validator

Fusion-Task-Id: FN-4621
Fusion-Task-Lineage: fc1b0b13-9052-4378-86e3-3634d6c9db4e

packages/core/src/__tests__/worktrunk-settings.test.ts

@@ -0,0 +1,56 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  resolveWorktrunkSettings,
+  validateWorktrunkSettings,
+} from "../worktrunk-settings.js";
+
+describe("worktrunk-settings", () => {
+  it("returns defaults when settings are empty", () => {
+    expect(resolveWorktrunkSettings({}, {})).toEqual({
+      enabled: false,
+      onFailure: "fail",
+    });
+  });
+
+  it("lets project enabled override global enabled", () => {
+    expect(resolveWorktrunkSettings({ enabled: false }, { enabled: true })).toEqual({
+      enabled: true,
+      onFailure: "fail",
+    });
+  });
+
+  it("retains global binaryPath when project only sets enabled", () => {
+    expect(
+      resolveWorktrunkSettings(
+        { enabled: false, binaryPath: "/x", onFailure: "fail" },
+        { enabled: true },
+      ),
+    ).toEqual({
+      enabled: true,
+      binaryPath: "/x",
+      onFailure: "fail",
+    });
+  });
+
+  it("falls back to defaults when both scopes are undefined", () => {
+    expect(resolveWorktrunkSettings(undefined, undefined)).toEqual({
+      enabled: false,
+      onFailure: "fail",
+    });
+  });
+
+  it("validator rejects invalid values", () => {
+    expect(() => validateWorktrunkSettings({ onFailure: "ignore" })).toThrow(
+      "worktrunk.onFailure must be one of",
+    );
+    expect(() => validateWorktrunkSettings({ binaryPath: 123 })).toThrow(
+      "worktrunk.binaryPath must be a string when set",
+    );
+    expect(() => validateWorktrunkSettings("oops")).toThrow("worktrunk settings must be an object");
+  });
+
+  it("validator drops unknown keys", () => {
+    expect(validateWorktrunkSettings({ enabled: true, unknown: "x" })).toEqual({ enabled: true });
+  });
+});