feat(research): streamline template details and enable bot versioning

backend/app/research/experiments.py

@@ -148,16 +148,25 @@ class Experiments:
         )
         variables = {}
         for name, variable in template.variables.items():
+            values = variable.values
+            # Empty field definitions bind only to the selected immutable input scope.
+            # Existing explicit domains remain restrictions and are never silently widened.
             if variable.kind == "field":
-                for value in variable.values:
+                if not values:
+                    values = sorted(field for field, kind in fields.items() if kind == variable.field_type)
+                if not values:
+                    raise HTTPException(422, f"变量 {name} 没有匹配的 {variable.field_type} 字段，请调整数据准备")
+                for value in values:
                     if fields.get(str(value)) != variable.field_type:
                         raise HTTPException(422, f"变量 {name} 的字段 {value} 不在固定输入中或类型不符")
             if variable.kind == "group" and any(
                 str(v) not in GROUPS and fields.get(str(v)) != "GROUP" for v in variable.values
             ):
                 raise HTTPException(422, f"分组变量 {name} 未在固定输入中核实")
+            if not values:
+                raise HTTPException(422, f"变量 {name} 缺少候选取值，请通过模板接口补充，或将固定参数直接写入表达式")
             variables[name] = [
-                json.dumps(v, ensure_ascii=False) if variable.kind == "string" else v for v in variable.values
+                json.dumps(v, ensure_ascii=False) if variable.kind == "string" else v for v in values
             ]
         try:
             expanded = expand(template.expression, variables, body.mode, body.limit, body.seed)