✅ test(settings-api): add test harness for proper isolation

- create createSettingsApiHarness function with temp directory setup
- add beforeEach/afterEach hooks for storage reset between tests
- add after hook for cleanup
- use dynamic imports after env setup to ensure proper initialization

tests/unit/settings-api.test.ts

@@ -1,34 +1,88 @@
-import { describe, test } from "node:test";
+import { describe, test, beforeEach, afterEach, after } from "node:test";
 import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+// --- Create harness function (similar to _chatPipelineHarness pattern) ---
+async function createSettingsApiHarness() {
+  const testDataDir = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-settings-api-"));
+  process.env.DATA_DIR = testDataDir;
+  process.env.REQUIRE_API_KEY = "false";
+  if (!process.env.API_KEY_SECRET) {
+    process.env.API_KEY_SECRET = "test-settings-api-secret-" + Date.now();
+  }
+
+  // --- Dynamic imports AFTER env setup ---
+  const core = await import("../../src/lib/db/core.ts");
+  const { getSettings, updateSettings } = await import("../../src/lib/db/settings.ts");
+  const settingsRoute = await import("../../src/app/api/settings/route.ts");
+
+  async function resetStorage() {
+    core.resetDbInstance();
+    fs.rmSync(testDataDir, { recursive: true, force: true });
+    fs.mkdirSync(testDataDir, { recursive: true });
+  }
+
+  function cleanup() {
+    core.resetDbInstance();
+    fs.rmSync(testDataDir, { recursive: true, force: true });
+  }
+
+  return {
+    testDataDir,
+    core,
+    getSettings,
+    updateSettings,
+    settingsRoute,
+    resetStorage,
+    cleanup,
+  };
+}
+
+// --- Initialize harness ---
+const harness = await createSettingsApiHarness();
+
+// --- Static import for helper (doesn't depend on DB) ---
 import { makeManagementSessionRequest } from "../helpers/managementSession.ts";
-import { getSettings, updateSettings } from "../../src/lib/db/settings.ts";
-const settingsRoute = await import("../../src/app/api/settings/route.ts");
+
+beforeEach(async () => {
+  await harness.resetStorage();
+});
+
+afterEach(async () => {
+  await harness.resetStorage();
+});
+
+after(() => {
+  harness.cleanup();
+});
 
 describe("Settings API - debugMode and hiddenSidebarItems", () => {
   describe("debugMode", () => {
     test("updateSettings with debugMode=true succeeds", async () => {
-      const result = await updateSettings({ debugMode: true });
+      const result = await harness.updateSettings({ debugMode: true });
       assert.ok(result, "updateSettings should return truthy result");
 
-      const settings = await getSettings();
+      const settings = await harness.getSettings();
       assert.strictEqual(settings.debugMode, true, "debugMode should be true");
     });
 
     test("updateSettings with debugMode=false succeeds", async () => {
-      const result = await updateSettings({ debugMode: false });
+      const result = await harness.updateSettings({ debugMode: false });
       assert.ok(result, "updateSettings should return truthy result");
 
-      const settings = await getSettings();
+      const settings = await harness.getSettings();
       assert.strictEqual(settings.debugMode, false, "debugMode should be false");
     });
   });
 
   describe("hiddenSidebarItems", () => {
     test("updateSettings with hiddenSidebarItems=['translator'] succeeds", async () => {
-      const result = await updateSettings({ hiddenSidebarItems: ["translator"] });
+      const result = await harness.updateSettings({ hiddenSidebarItems: ["translator"] });
       assert.ok(result, "updateSettings should return truthy result");
 
-      const settings = await getSettings();
+      const settings = await harness.getSettings();
       assert.deepStrictEqual(
         settings.hiddenSidebarItems,
         ["translator"],
@@ -37,10 +91,10 @@ describe("Settings API - debugMode and hiddenSidebarItems", () => {
     });
 
     test("updateSettings with empty hiddenSidebarItems succeeds", async () => {
-      const result = await updateSettings({ hiddenSidebarItems: [] });
+      const result = await harness.updateSettings({ hiddenSidebarItems: [] });
       assert.ok(result, "updateSettings should return truthy result");
 
-      const settings = await getSettings();
+      const settings = await harness.getSettings();
       assert.deepStrictEqual(
         settings.hiddenSidebarItems,
         [],
@@ -51,13 +105,13 @@ describe("Settings API - debugMode and hiddenSidebarItems", () => {
 
   describe("combined updates", () => {
     test("updateSettings with both debugMode and hiddenSidebarItems succeeds", async () => {
-      const result = await updateSettings({
+      const result = await harness.updateSettings({
         debugMode: true,
         hiddenSidebarItems: ["translator"],
       });
       assert.ok(result, "updateSettings should return truthy result");
 
-      const settings = await getSettings();
+      const settings = await harness.getSettings();
       assert.strictEqual(settings.debugMode, true, "debugMode should be true");
       assert.deepStrictEqual(
         settings.hiddenSidebarItems,
@@ -67,12 +121,12 @@ describe("Settings API - debugMode and hiddenSidebarItems", () => {
     });
 
     test("updateSettings persists antigravitySignatureCacheMode", async () => {
-      const result = await updateSettings({
+      const result = await harness.updateSettings({
         antigravitySignatureCacheMode: "bypass-strict",
       });
       assert.ok(result, "updateSettings should return truthy result");
 
-      const settings = await getSettings();
+      const settings = await harness.getSettings();
       assert.strictEqual(
         settings.antigravitySignatureCacheMode,
         "bypass-strict",
@@ -81,7 +135,7 @@ describe("Settings API - debugMode and hiddenSidebarItems", () => {
     });
 
     test("PUT /api/settings reuses the PATCH update flow", async () => {
-      const response = await settingsRoute.PUT(
+      const response = await harness.settingsRoute.PUT(
         await makeManagementSessionRequest("http://localhost/api/settings", {
           method: "PUT",
           body: { antigravitySignatureCacheMode: "bypass" },