fix: 数据源审查小修（from_config 类型守卫/PROMPTS_KEYS 消重/契约措辞）

Co-Authored-By: Claude Code <noreply@anthropic.com>

tests/test_db_tenant_source.py

@@ -20,7 +20,7 @@ import pytest
 from sqlalchemy import text
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from app.engine.services.ai_service import PromptProvider
+from app.engine.services.ai_service import PROMPTS_KEYS, PromptProvider
 from app.platform.db import (
     Site,
     SiteDomain,
@@ -36,8 +36,6 @@ REPO_ROOT = Path(__file__).resolve().parents[1]
 SEED_DIR = REPO_ROOT / "seed_profiles"
 JC_DOMAIN = "db.jc.example.com"      # DB 源测试专属域名(不与文件源种子撞)
 
-_PROMPTS_KEYS = ("system", "company_facts", "extractor", "evaluator")
-
 
 def _jiancai_snapshot(prefix="ai-kefu-jc"):
     """版本 config_json 构造助手:seed jiancai 的 config 组 + wall.json +
@@ -51,7 +49,7 @@ def _jiancai_snapshot(prefix="ai-kefu-jc"):
         (SEED_DIR / "jiancai" / "wall.json").read_text(encoding="utf-8"))
     snapshot["prompts"] = {
         name: (prompts_dir / f"{name}.md").read_text(encoding="utf-8")
-        for name in _PROMPTS_KEYS
+        for name in PROMPTS_KEYS
     }
     return snapshot