feat: add cheater gate with resume-safe survivor recovery

app/question_gen/adversarial_filter.py

@@ -12,6 +12,14 @@ from __future__ import annotations
 import enum
 import hashlib
 import json
+from typing import TYPE_CHECKING, Protocol
+
+from loguru import logger
+
+if TYPE_CHECKING:
+    from app.question_gen.adversarial_config import AdversarialFilterConfig
+    from app.question_gen.run_store import QuestionGenStore
+    from core.types import GeneratedQuestion
 
 _VALID_LETTERS = ("A", "B", "C", "D")
 
@@ -94,3 +102,114 @@ def judge_flip(*, p_text: str | None, q_text: str | None) -> FlipDecision:
     if p_text.strip() != q_text.strip():
         return FlipDecision.PASSED
     return FlipDecision.FILTERED_NO_FLIP
+
+
+class AgentRunner(Protocol):
+    """完整 inference agent 试答端口 — Phase B 只依赖此接口（便于 mock）。
+
+    实现见 Task 10 的 _RealAgentRunner（复用 run_inference + RunLogImpl）。
+    """
+
+    model: str
+    skill_mode: str  # 从首次定义即入 Protocol，保证 Task 6/8/10 指纹口径一致
+
+    async def predict(
+        self,
+        questions: list[GeneratedQuestion],
+        *,
+        max_steps: int,
+        run_id: str,
+    ) -> dict[str, str | None]:
+        """跑完整 agent，返回 question_id → 预测答案字母（无预测为 None）。"""
+        ...
+
+
+def _cheat_hash(question: GeneratedQuestion) -> str:
+    """按散参数签名计算作弊门题面 hash（question/options/answer）。"""
+    return question_hash(question.question, question.options, question.answer)
+
+
+def _recover_survivors(
+    questions: list[GeneratedQuestion],
+    store: QuestionGenStore,
+    cfg_fp: str,
+) -> list[GeneratedQuestion]:
+    """从已落 cheat verdict 恢复"agent 答错"的题（续跑，不重跑 agent）。"""
+    survivors: list[GeneratedQuestion] = []
+    for q in questions:
+        rows = store._conn.execute(
+            "SELECT agent_correct FROM adversarial_verdicts "
+            "WHERE question_id=? AND question_hash=? AND stage='cheat' AND agent_config=?",
+            (q.question_id, _cheat_hash(q), cfg_fp),
+        ).fetchall()
+        if rows and rows[0][0] == 0:
+            survivors.append(q)
+    return survivors
+
+
+async def run_cheater_gate(
+    questions: list[GeneratedQuestion],
+    *,
+    agent: AgentRunner,
+    store: QuestionGenStore,
+    config: AdversarialFilterConfig,
+    round_no: int,
+    run_id: str,
+) -> list[GeneratedQuestion]:
+    """作弊门：完整 agent 试答；答对→filtered_too_easy，答错→cheat passed 待翻转。
+
+    续跑：已在当前 hash+config 有 cheat verdict 的题跳过重跑。agent_config 变
+    化时先作废该题旧 verdict。预测立即落表（崩溃不丢）。
+
+    参数:
+        questions: 待判定的 AR 题列表。
+        agent: 完整 agent 试答端口。
+        store: verdict 持久化。
+        config: 过滤配置（提供 max_steps）。
+        round_no: 当前轮次。
+        run_id: agent 推理 run 标识。
+
+    返回:
+        agent 答错的题（进翻转门）——含"已完成续跑恢复的存活者"与"本轮新判答错者"
+        两部分合并。答错题的 cheat 预测字母已落 adversarial_verdicts 表
+        （stage='cheat'），翻转门经 `_read_cheat_prediction` 从表读取复用（不重跑）。
+    """
+    cfg_fp = agent_config_fingerprint(
+        skill_mode=agent.skill_mode,
+        max_steps=config.adversarial_agent_max_steps,
+        model=agent.model,
+    )
+    todo: list[GeneratedQuestion] = []
+    completed: list[GeneratedQuestion] = []
+    for q in questions:
+        h = _cheat_hash(q)
+        store.invalidate_stale_config(q.question_id, cfg_fp)
+        if "cheat" in store.completed_stages(q.question_id, h, cfg_fp):
+            completed.append(q)
+        else:
+            todo.append(q)
+
+    # C1: 无条件先从已完成题恢复存活者（agent 答错），再对未判题跑 agent 追加。
+    # 两者都流向翻转门——绝不因 todo 非空而丢掉已完成的存活者（混合续跑正确性）。
+    survivors: list[GeneratedQuestion] = _recover_survivors(completed, store, cfg_fp)
+
+    if todo:
+        preds = await agent.predict(
+            todo, max_steps=config.adversarial_agent_max_steps, run_id=run_id
+        )
+        for q in todo:
+            pred = preds.get(q.question_id)
+            correct = pred is not None and pred.strip().upper() == q.answer.strip().upper()
+            verdict = "filtered_too_easy" if correct else "passed"
+            store.record_verdict(
+                question_id=q.question_id, question_hash=_cheat_hash(q), stage="cheat",
+                round=round_no, agent_prediction=pred, agent_correct=correct,
+                verdict=verdict, pair_id=None, agent_config=cfg_fp,
+            )
+            if not correct:
+                survivors.append(q)
+    logger.info(
+        "作弊门: {} 题（续跑复用 {}，新判 {}）→ 存活 {}",
+        len(questions), len(completed), len(todo), len(survivors),
+    )
+    return survivors