refactor(search)!: /ask 고아 service·테스트·프롬프트 정리 (검색 단일화 Phase 2)

/ask 삭제로 0-consumer 된 자산 제거(3-gate 실증): search.py /ask 섹션(Citation/ConfirmedItem/AskDebug/AskResponse 모델 + 헬퍼 + _resolve_eval_identity) + 죽은 import 13개. service 4(classifier/verifier/refusal_gate/grounding_check). AIClient.call_classifier/call_verifier(고아). 프롬프트 2(classifier/verifier.txt). broken test 6. evidence/synthesis 는 공유(documents.py 등)라 유지. 실 pyflakes 클린(이전 세션 pyflakes 미설치로 검증 누락 → 설치 후 실검증).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/search.py

@@ -3,42 +3,28 @@
 실제 검색 파이프라인(retrieval → fusion → rerank → diversity → confidence)
 은 `services/search/search_pipeline.py::run_search()` 로 분리되어 있다.
 이 파일은 다음만 담당:
-  - Pydantic 스키마 (SearchResult / SearchResponse / SearchDebug / DebugCandidate
-    / Citation / AskResponse / AskDebug)
+  - Pydantic 스키마 (SearchResult / SearchResponse / SearchDebug / DebugCandidate)
   - `/search` endpoint wrapper (run_search 호출 + logger + telemetry + 직렬화)
-  - `/ask` endpoint wrapper (Phase 3.3 에서 추가)
 """
 
-import asyncio
-import hmac
-import time
 from datetime import date
-from typing import Annotated, Literal
+from typing import Annotated
 
-from fastapi import APIRouter, BackgroundTasks, Depends, Header, Query
+from fastapi import APIRouter, BackgroundTasks, Depends, Query
 from fastapi.responses import JSONResponse
 from pydantic import BaseModel
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from core.auth import get_current_user
-from core.config import settings
 from core.database import get_session
 from core.utils import setup_logger
 from models.user import User
-from services.document_telemetry import sanitize_source
-from services.search.classifier_service import ClassifierResult, classify
-from services.search.evidence_service import EvidenceItem, extract_evidence
 from services.search.fusion_service import DEFAULT_FUSION
-from services.search.grounding_check import check as grounding_check
-from services.search.refusal_gate import RefusalDecision, decide as refusal_decide
 from services.search import query_rewriter
 from services.search.retrieval_service import AxisFilter
 from services.search.result_decorate import compute_facets, decorate_version_status
 from services.search.search_pipeline import PipelineResult, run_search
-from services.search.synthesis_service import SynthesisResult, synthesize
-from services.search.verifier_service import VerifierResult, verify
-from services.prompt_versions import ASK_PROMPT_VERSION, resolve_primary_model
-from services.search_telemetry import record_ask_event, record_search_event
+from services.search_telemetry import record_search_event
 
 # logs/search.log + stdout 동시 출력 (Phase 0.4)
 logger = setup_logger("search")
@@ -354,241 +340,3 @@ async def search(
         debug=debug_obj,
         facets=facets_obj,
     )
-
-
-# ═══════════════════════════════════════════════════════════
-# Phase 3.3: /api/search/ask — Evidence + Grounded Synthesis
-# ═══════════════════════════════════════════════════════════
-
-
-class Citation(BaseModel):
-    """answer 본문의 [n] 에 해당하는 근거 단일 행."""
-
-    n: int
-    chunk_id: int | None
-    doc_id: int
-    title: str | None
-    section_title: str | None
-    span_text: str  # evidence LLM 이 추출한 50~300자
-    full_snippet: str  # 원본 800자 (citation 원문 보기 전용)
-    relevance: float
-    rerank_score: float
-
-
-class ConfirmedItem(BaseModel):
-    """Partial answer 의 개별 aspect 답변."""
-
-    aspect: str
-    text: str
-    citations: list[int]
-
-
-class AskDebug(BaseModel):
-    """`/ask?debug=true` 응답 확장."""
-
-    timing_ms: dict[str, float]
-    search_notes: list[str]
-    query_analysis: dict | None = None
-    confidence_signal: float
-    evidence_candidate_count: int
-    evidence_kept_count: int
-    evidence_skip_reason: str | None
-    synthesis_cache_hit: bool
-    synthesis_prompt_preview: str | None = None
-    synthesis_raw_preview: str | None = None
-    hallucination_flags: list[str] = []
-    # Phase 3.5a: per-layer defense 로깅
-    defense_layers: dict | None = None
-
-
-class AskResponse(BaseModel):
-    """`/ask` 응답. Phase 3.5a: completeness + aspects 추가."""
-
-    results: list[SearchResult]
-    ai_answer: str | None
-    citations: list[Citation]
-    synthesis_status: Literal[
-        "completed", "timeout", "skipped", "no_evidence", "parse_failed", "llm_error",
-        # PR-MacBook-RAG-Backend-1: 200 응답에는 등장하지 않음 (해당 status 는 503 분기).
-        # Literal 호환성 위해 포함.
-        "backend_unavailable",
-    ]
-    synthesis_ms: float
-    confidence: Literal["high", "medium", "low"] | None
-    refused: bool
-    no_results_reason: str | None
-    query: str
-    total: int
-    # Phase 3.5a
-    completeness: Literal["full", "partial", "insufficient"] = "full"
-    covered_aspects: list[str] | None = None
-    missing_aspects: list[str] | None = None
-    confirmed_items: list[ConfirmedItem] | None = None
-    # PR-MacBook-RAG-Backend-1: backend dispatcher metadata.
-    # backend 미지정 호출은 둘 다 None 으로 유지 (기존 호출자 호환 — Hermes docsrv_ask /
-    # voice-memo-bot 응답 형식 변동 0). 명시 opt-in 시만 채워짐.
-    backend_requested: str | None = None
-    backend_used: str | None = None
-    debug: AskDebug | None = None
-
-
-def _map_no_results_reason(
-    pr: PipelineResult,
-    evidence: list[EvidenceItem],
-    ev_skip: str | None,
-    sr: SynthesisResult,
-) -> str | None:
-    """사용자에게 보여줄 한국어 메시지 매핑.
-
-    Failure mode 표 (plan §Failure Modes) 기반.
-    """
-    # LLM 자가 refused → 모델이 준 사유 그대로
-    if sr.refused and sr.refuse_reason:
-        return sr.refuse_reason
-
-    # synthesis 상태 우선
-    if sr.status == "no_evidence":
-        if not pr.results:
-            return "검색 결과가 없습니다."
-        return "관련도 높은 근거를 찾지 못했습니다."
-    if sr.status == "skipped":
-        return "검색 결과가 없습니다."
-    if sr.status == "timeout":
-        return "답변 생성이 지연되어 생략했습니다. 검색 결과를 확인해 주세요."
-    if sr.status == "parse_failed":
-        return "답변 형식 오류로 생략했습니다."
-    if sr.status == "llm_error":
-        return "AI 서버에 일시적 문제가 있습니다."
-
-    # evidence 단계 실패는 fallback 을 탔더라도 notes 용
-    if ev_skip == "all_low_rerank":
-        return "관련도 높은 근거를 찾지 못했습니다."
-    if ev_skip == "empty_retrieval":
-        return "검색 결과가 없습니다."
-
-    return None
-
-
-def _build_citations(
-    evidence: list[EvidenceItem], used_citations: list[int]
-) -> list[Citation]:
-    """answer 본문에 실제로 등장한 n 만 Citation 으로 변환."""
-    by_n = {e.n: e for e in evidence}
-    out: list[Citation] = []
-    for n in used_citations:
-        e = by_n.get(n)
-        if e is None:
-            continue
-        out.append(
-            Citation(
-                n=e.n,
-                chunk_id=e.chunk_id,
-                doc_id=e.doc_id,
-                title=e.title,
-                section_title=e.section_title,
-                span_text=e.span_text,
-                full_snippet=e.full_snippet,
-                relevance=e.relevance,
-                rerank_score=e.rerank_score,
-            )
-        )
-    return out
-
-
-def _build_ask_debug(
-    pr: PipelineResult,
-    evidence: list[EvidenceItem],
-    ev_skip: str | None,
-    sr: SynthesisResult,
-    ev_ms: float,
-    synth_ms: float,
-    total_ms: float,
-) -> AskDebug:
-    timing: dict[str, float] = dict(pr.timing_ms)
-    timing["evidence_ms"] = ev_ms
-    timing["synthesis_ms"] = synth_ms
-    timing["ask_total_ms"] = total_ms
-
-    # candidate count 는 rule filter 통과한 수 (recomputable from results)
-    # 엄밀히는 evidence_service 내부 숫자인데, evidence 길이 ≈ kept, candidate
-    # 는 관측이 어려움 → kept 는 evidence 길이, candidate 는 별도 필드 없음.
-    # 단순화: candidate_count = len(evidence) 를 상한 근사로 둠 (debug 전용).
-    return AskDebug(
-        timing_ms=timing,
-        search_notes=pr.notes,
-        query_analysis=pr.query_analysis,
-        confidence_signal=pr.confidence_signal,
-        evidence_candidate_count=len(evidence),
-        evidence_kept_count=len(evidence),
-        evidence_skip_reason=ev_skip,
-        synthesis_cache_hit=sr.cache_hit,
-        synthesis_prompt_preview=None,  # 현재 synthesis_service 에서 노출 안 함
-        synthesis_raw_preview=sr.raw_preview,
-        hallucination_flags=sr.hallucination_flags,
-    )
-
-
-def _detect_synthesis_failure(sr: SynthesisResult) -> str | None:
-    """Synthesis 가 유효한 답을 못 냈으면 re_gate 라벨, 아니면 None.
-
-    판정 우선순위 (Phase 3.5 fix3):
-      1) sr.refused → LLM self-refuse (status="completed") 또는 mechanical fail 후 refused 전파
-         - status=="completed" + refused=True → "synthesis_self_refuse"
-         - 그 외 → f"synthesis_failed({status})"
-      2) sr.status ∈ {timeout, parse_failed, llm_error} → f"synthesis_failed({status})"
-      3) answer 공백 → f"synthesis_failed({status})"
-      4) 유효 → None
-    """
-    if sr.refused:
-        if sr.status == "completed":
-            return "synthesis_self_refuse"
-        return f"synthesis_failed({sr.status})"
-    if sr.status in ("timeout", "parse_failed", "llm_error"):
-        return f"synthesis_failed({sr.status})"
-    if not (sr.answer or "").strip():
-        return f"synthesis_failed({sr.status})"
-    return None
-
-
-def _resolve_eval_identity(
-    x_source: str | None,
-    x_eval_case_id: str | None,
-    x_eval_token: str | None,
-) -> tuple[str, str | None]:
-    """X-Source/X-Eval-Case-Id 신뢰 검증 (Phase 3.5 fix2).
-
-    규칙:
-      - 기본값: source='document_server', eval_case_id=None
-      - X-Source=eval 또는 X-Eval-Case-Id 가 들어왔다면 eval claim 으로 간주
-      - eval claim 은 X-Eval-Token == settings.eval_runner_token 일 때만 수용
-        (constant-time compare, env 미설정 시 항상 거부)
-      - 거부 시: 헤더 무시 + warning log + source=sanitize(non-eval) / eval_case_id=None
-      - 통과 시: source='eval', eval_case_id=x_eval_case_id
-
-    반환: (source, eval_case_id)
-    """
-    claimed_source = sanitize_source(x_source)
-    is_eval_claim = (claimed_source == "eval") or bool(x_eval_case_id)
-    if not is_eval_claim:
-        # 일반 호출 — eval_case_id 강제 None (source != 'eval' 이면 case_id 의미 없음)
-        return claimed_source, None
-
-    # eval claim — token 검증
-    expected = settings.eval_runner_token
-    presented = x_eval_token or ""
-    token_valid = bool(expected) and hmac.compare_digest(presented, expected)
-    if not token_valid:
-        logger.warning(
-            "eval header rejected: source=%s case_id=%s token_present=%s expected_set=%s",
-            x_source, x_eval_case_id, bool(x_eval_token), bool(expected),
-        )
-        # 일반 호출로 강등 — source='eval' 주장은 무시, case_id 도 무시
-        # claimed_source 가 'eval' 이면 default 'document_server' 로
-        if claimed_source == "eval":
-            return "document_server", None
-        return claimed_source, None
-
-    # token OK — eval 라벨 수용
-    return "eval", x_eval_case_id
-
-