fix: tolerate backfill under-delivery, fix predict None-fill, drop dead session_id

tests/integration/test_adversarial_filter_e2e.py

@@ -275,3 +275,27 @@ async def test_real_agent_runner_predict_roundtrips_predictions(tmp_path: Path)
         "smoke_r0", question_ids=["smoke"]
     )
     assert rows and rows[0]["prediction"] == "B"
+
+
+@pytest.mark.asyncio
+async def test_real_agent_runner_predict_fills_none_for_missing(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """predict 对 predictions 表缺失的 qid 返回 None（契约：每个入参 qid 都有键）。"""
+
+    async def _noop_run_inference(*args: Any, **kwargs: Any) -> None:
+        """空跑：不写 predictions 表，模拟回读缺行。"""
+        return None
+
+    monkeypatch.setattr("app.harness.inference.run_inference", _noop_run_inference)
+    runner = _RealAgentRunner(
+        llm=_MockLLM(answer="B"),
+        tool_dispatch_fn=lambda *a, **k: None,
+        prompt_builder=lambda q: ("s", "u"),
+        db_path=str(tmp_path / "harness.db"),
+        concurrency=1,
+        skill_mode="none",
+        model="mock",
+    )
+    preds = await runner.predict([_smoke_q("missing")], max_steps=1, run_id="r_none")
+    assert preds == {"missing": None}  # 缺回读行 → 该 qid 键存在且为 None