Prompt (rr-iter2-001): Implement a negative-trigger whitelist in `gate-3-classifier.ts` and run the targeted tests.
Expected skill: sk-code

Advisor output:
[
  {
    "skill": "sk-code",
    "kind": "skill",
    "confidence": 0.8561,
    "uncertainty": 0.12,
    "passes_threshold": true,
    "reason": "Matched by native advisor_recommend",
    "source": "native",
    "score": 0.656542,
    "dominant_lane": "explicit_author",
    "status": "active",
    "_shadow": {
      "skillId": "sk-code",
      "liveScore": 0.656542,
      "shadowScore": 0.581194,
      "delta": -0.075348,
      "dominantShadowLane": "explicit_author"
    }
  }
]
