test(rag): 补充引擎懒构建与 HTTP 级 RAG e2e 覆盖，恢复 99% 门禁

tests/test_impact_rag_e2e.py

@@ -8,10 +8,14 @@ from __future__ import annotations
 import asyncio
 import glob
 import io
+import json
 import zipfile
 from pathlib import Path
 
 import pytest
+from fastapi.testclient import TestClient
+
+from genesis.server.app import create_app
 
 from genesis.impact.impact_agent import _RAG_CONTEXT_TITLE
 from genesis.rag.embeddings import FakeEmbedder
@@ -144,3 +148,77 @@ def test_rag_e2e_use_rag_false_backward_compat(tmp_path):
     assert _RAG_CONTEXT_TITLE not in (engine.captured or "")
     # 确定性报告存在
     assert rec.impact_report_path and Path(rec.impact_report_path).exists()
+
+
+def test_service_rag_lazy_engine_build(tmp_path, monkeypatch):
+    """覆盖 service.py:233-236：构造未传 engine 且 run_impact(use_rag=True) 时懒构建引擎。"""
+    store = SessionStore(db_path=str(tmp_path / "s.db"))
+    rag = ImpactRAG(RagStore(str(tmp_path / "rag.db")), FakeEmbedder())
+    # 注入的懒构建产物：一个会捕获 prompt 的 FakeEngine
+    injected_engine = FakeEngine()
+    monkeypatch.setattr(
+        "genesis.inference.factory.build_inference_engine", lambda: injected_engine
+    )
+    svc = GenesisService(
+        store=store,
+        data_root=str(tmp_path / "data"),
+        rag=rag,
+        use_rag=False,  # 构造时不传 engine、RAG 默认关闭
+    )
+    assert svc.engine is None  # 尚未构建
+
+    sid = svc.create_session("u1").session_id
+    svc.upload_file(sid, "requirements", "requirements_newdev.xlsx", _sample_req())
+    svc.upload_file(sid, "template", "template_design_ja.docx", _sample_tpl())
+    # 上传即索引（D1），existing_system 含 KnownOrder 源码
+    svc.upload_file(sid, "existing_system", "existing.zip", _make_existing_zip())
+    svc.run_parse(sid)
+    svc.confirm_parse(sid)
+    assert svc.get_session(sid).status == "impact_running"
+
+    # 显参开启 RAG → 触发 engine 为 None 的懒构建分支
+    rec = asyncio.run(svc.run_impact(sid, use_rag=True))
+    assert rec.status == "awaiting_impact_confirm"
+    # 懒构建的引擎被注入并实际使用
+    assert svc.engine is injected_engine
+    summary = json.loads(rec.impact_summary)
+    assert summary.get("rag_enabled") is True
+    # 引擎捕获的 prompt 含 RAG 检索注入的 KnownOrder 片段
+    assert injected_engine.captured is not None
+    assert "KnownOrder" in injected_engine.captured
+
+
+def test_http_start_impact_use_rag_e2e(tmp_path):
+    """覆盖 app.py start_impact 异步端点 + _FakeEngine.chat_structured（RAG 路径，HTTP 级）。"""
+    store = SessionStore(db_path=str(tmp_path / "s.db"))
+    rag = ImpactRAG(RagStore(str(tmp_path / "rag.db")), FakeEmbedder())
+    app = create_app(
+        store=store,
+        data_root=str(tmp_path / "data"),
+        engine="fake",  # 触发内部 _FakeEngine（异步 chat_structured）
+        rag=rag,
+    )
+    client = TestClient(app)
+
+    sid = client.post("/api/sessions", json={"user_id": "u1"}).json()["session_id"]
+    # multipart 上传：要件/模板/既有系统
+    client.post(f"/api/sessions/{sid}/files",
+                data={"file_type": "requirements"},
+                files={"file": ("requirements_newdev.xlsx", _sample_req())})
+    client.post(f"/api/sessions/{sid}/files",
+                data={"file_type": "template"},
+                files={"file": ("template_design_ja.docx", _sample_tpl())})
+    client.post(f"/api/sessions/{sid}/files",
+                data={"file_type": "existing_system"},
+                files={"file": ("existing.zip", _make_existing_zip())})
+
+    assert client.post(f"/api/sessions/{sid}/start-parse").status_code == 200
+    # 有既有系统 → impact_running
+    assert client.post(f"/api/sessions/{sid}/confirm-parse").json()["status"] == "impact_running"
+
+    # 异步端点：start-impact?use_rag=True（显参开启 RAG）
+    r = client.post(f"/api/sessions/{sid}/start-impact?use_rag=True")
+    assert r.status_code == 200
+    ir = client.get(f"/api/sessions/{sid}/impact-result").json()
+    # 经 HTTP 真实走到 RAG 路径，摘要标记 rag_enabled
+    assert ir.get("rag_enabled") is True