fix(P0-03): Prediction 幂等指纹——只追加,不覆盖

_upsert_prediction 改为 _insert_or_find_by_fingerprint:
- 同 input_hash → 返回已有行(绝不 UPDATE pred_/reasoning/agent_outputs)
- 不同 input_hash → INSERT 新行

input_hash 升级为规范 JSON SHA-256,捕获:match_id, cutoff, prompt_version,
prompt_hash, system_prompt_hash, provider, model, mode, run_type, temperature,
context_hash, agent_ids。移除旧 (match, provider, model, mode, run_type) 唯一约束,
改为 partial unique index(WHERE input_hash IS NOT NULL,兼容旧 NULL 数据)。

三条路径(single/multi/baseline)统一传足指纹字段。
迁移 0024 + 测试 test_p0_prediction_fingerprint(10/10);全量 295 通过。

tests/test_prediction_unique_constraint.py

@@ -3,7 +3,7 @@
 验证:
   1. 唯一约束包含 mode + run_type
   2. 同一场比赛 live 与 backtest 预测可共存,互不覆盖
-  3. _upsert_prediction 正确区分 run_type
+  3. _insert_or_find_by_fingerprint 正确区分 run_type
 """
 from __future__ import annotations
 
@@ -12,6 +12,7 @@ from pathlib import Path
 
 from pydantic import BaseModel
 import pytest
+from sqlalchemy import Index
 
 from src.db.models import Prediction, UniqueConstraint, CheckConstraint
 
@@ -22,20 +23,32 @@ MIGRATION_PATH = REPO_ROOT / "alembic" / "versions" / "0013_predictions_unique_c
 
 
 class TestUniqueConstraint:
-    """验证唯一约束包含 mode + run_type。"""
+    """P0-03: 验证幂等指纹唯一索引(替代旧 (match, provider, model, mode, run_type) 唯一约束)。"""
 
-    def test_constraint_columns(self):
-        """唯一约束应包含 match_id, provider, model, mode, run_type。"""
-        uc = [
-            c for c in Prediction.__table__.constraints
-            if isinstance(c, UniqueConstraint) and "match" in c.name
+    def test_input_hash_partial_unique_index(self):
+        """P0-03: input_hash 非空时必须唯一(同指纹 → 返回已有行,不 UPDATE/INSERT)。"""
+        idx = [
+            i for i in Prediction.__table__.indexes
+            if i.unique and "input_hash" in i.name
         ]
-        assert len(uc) == 1
-        cols = [c.name for c in uc[0].columns]
-        assert cols == ["match_id", "provider", "model", "mode", "run_type"]
+        assert len(idx) == 1, f"缺少 input_hash partial unique 索引,现有 indexes: {[i.name for i in Prediction.__table__.indexes]}"
+        # partial unique: postgresql_where 必须限制 input_hash IS NOT NULL
+        assert idx[0].dialect_kwargs.get("postgresql_where") is not None
+
+    def test_old_unique_constraint_removed(self):
+        """P0-03: 旧 (match, provider, model, mode, run_type) 唯一约束必须已移除。"""
+        from sqlalchemy import UniqueConstraint
+
+        old = [
+            c for c in Prediction.__table__.constraints
+            if isinstance(c, UniqueConstraint) and c.name == "uq_predictions_match_provider_model_mode_run_type"
+        ]
+        assert len(old) == 0, f"旧约束必须已移除,但仍存在: {[c.name for c in old]}"
 
     def test_run_type_check_constraint(self):
         """应有 run_type 的 check constraint。"""
+        from sqlalchemy import CheckConstraint
+
         cc = [
             c for c in Prediction.__table__.constraints
             if isinstance(c, CheckConstraint) and "run_type" in c.name
@@ -52,13 +65,16 @@ class TestUniqueConstraint:
 
 
 class TestUpsertPredictionSignature:
-    """验证 _upsert_prediction 函数签名包含 run_type。"""
+    """验证 _insert_or_find_by_fingerprint 签名(P0-03 指纹模式)。"""
 
-    def test_signature_has_run_type(self):
-        from src.llm.predict import _upsert_prediction
+    def test_signature_uses_values_dict(self):
+        """P0-03: 新接口通过 values dict 接收全部字段(含 run_type/match_id/...)。"""
+        from src.llm.predict import _insert_or_find_by_fingerprint
 
-        sig = inspect.signature(_upsert_prediction)
-        assert "run_type" in sig.parameters
+        sig = inspect.signature(_insert_or_find_by_fingerprint)
+        params = sig.parameters
+        assert "session" in params
+        assert "values" in params  # 所有业务字段走 values dict
 
     def test_signature_has_backtest_in_predict_match(self):
         from src.llm.predict import predict_match