feat(FN-5112): complete Step 3 — reviewer LLM defense-in-depth

Fusion-Task-Id: FN-5112
Fusion-Task-Lineage: 692fba2a-5856-4256-8144-d87bda56e1aa

packages/engine/src/__tests__/reviewer.test.ts

@@ -258,6 +258,7 @@ describe("reviewStep — spec review type", () => {
     expect(capturedPrompt).toContain("Evaluate this PROMPT.md specification");
     expect(capturedPrompt).toContain("spec quality criteria");
     expect(capturedPrompt).toContain("# Task: KB-050");
+    expect(capturedPrompt).toContain("dangling task-document references");
     // Spec reviews should NOT contain git diff instructions
     expect(capturedPrompt).not.toContain("git diff");
   });