Fix MBTI canonical result section registry

lib/mbti/publicProjection.ts

@@ -45,6 +45,8 @@ const RESULT_SECTION_ORDER = [
   "letters_intro",
   "overview",
   "trait_overview",
+  "traits.at_difference",
+  "faq",
   "traits.why_this_type",
   "traits.close_call_axes",
   "traits.adjacent_type_contrast",

tests/contracts/mbti-result-section-registry.contract.test.ts

@@ -0,0 +1,46 @@
+import { describe, expect, it } from "vitest";
+import type { ReportResponse } from "@/lib/api/v0_3";
+import { buildMbtiResultProjectionViewModel } from "@/lib/mbti/publicProjection";
+import reportReadyMbtiProjectionFixture from "@/tests/fixtures/report_ready.mbti.projection.json";
+
+describe("MBTI result section registry", () => {
+  it("preserves the canonical A/T difference and FAQ sections in inventory order", () => {
+    const report = structuredClone(reportReadyMbtiProjectionFixture) as ReportResponse;
+    const projection = report.mbti_public_projection_v1 as {
+      sections?: Array<Record<string, unknown>>;
+    };
+
+    projection.sections = [
+      ...(projection.sections ?? []),
+      {
+        key: "faq",
+        render: "bullets",
+        title: "Frequently asked questions",
+        payload: {
+          items: [{ question: "Synthetic question", answer: "Synthetic answer" }],
+        },
+      },
+      {
+        key: "traits.at_difference",
+        render: "rich_text",
+        title: "A/T identity layer",
+        body_md: "Synthetic A/T difference body.",
+      },
+    ];
+
+    const viewModel = buildMbtiResultProjectionViewModel(report);
+    const keys = viewModel.sections.map((section) => section.key);
+
+    expect(keys).toContain("traits.at_difference");
+    expect(keys).toContain("faq");
+    expect(keys.indexOf("trait_overview")).toBeLessThan(keys.indexOf("traits.at_difference"));
+    expect(keys.indexOf("traits.at_difference")).toBeLessThan(keys.indexOf("faq"));
+    expect(keys.indexOf("faq")).toBeLessThan(keys.indexOf("career.summary"));
+    expect(viewModel.sections.find((section) => section.key === "traits.at_difference")?.bodyMd).toBe(
+      "Synthetic A/T difference body."
+    );
+    expect(viewModel.sections.find((section) => section.key === "faq")?.payload).toMatchObject({
+      items: [{ question: "Synthetic question", answer: "Synthetic answer" }],
+    });
+  });
+});