feat: add durable WorldQuant backtests with UI and AI confirmation

backend/tests/ai_fake.py

@@ -17,6 +17,23 @@ async def fake_stream(messages, info):
         str(p.content) for m in messages[latest:] for p in m.parts if isinstance(p, UserPromptPart)
     )
     returns = [p for m in messages[latest:] for p in m.parts if isinstance(p, ToolReturnPart)]
+    if returns and returns[-1].tool_name == "prepare_backtest":
+        content = returns[-1].content
+        content = json.loads(content) if isinstance(content, str) else content
+        yield {
+            0: DeltaToolCall(
+                name="start_backtest",
+                json_args=json.dumps(
+                    {
+                        "preview_id": content["preview_id"],
+                        "version": 1,
+                        "idempotency_key": content["preview_id"],
+                    }
+                ),
+                tool_call_id=uuid4().hex,
+            )
+        }
+        return
     if returns and "LOOP" not in text:
         if returns[-1].tool_name == "capability_probe":
             yield str(returns[-1].content)
@@ -35,6 +52,23 @@ async def fake_stream(messages, info):
         await asyncio.sleep(2)
         yield "，查询完成。"
         return
+    elif "回测" in text:
+        name, args = (
+            "prepare_backtest",
+            {
+                "inline": {
+                    "name": "AI 固定回测",
+                    "source": {"kind": "ai"},
+                    "candidates": [
+                        {
+                            "client_item_id": "ai-1",
+                            "expression": "rank(close)",
+                            "settings": {"region": "USA", "universe": "TOP3000", "delay": 1},
+                        }
+                    ],
+                }
+            },
+        )
     elif "批量" in text:
         name, args = "bulk_update_research", {"alpha_ids": ["a0000", "a0001"], "add_tags": ["AI"]}
     elif "修改" in text or "update" in text: