feat: add deterministic message interaction stages

backend/schemas.py

@@ -100,9 +100,18 @@ class StartupAction(CamelModel):
     required: bool = True
 
 
+class OpeningMessageConfig(CamelModel):
+    """Built-in Prompt opening interaction; it is not a reusable LLM tool."""
+
+    title: str = Field(default="重要提示", min_length=1, max_length=120)
+    message: str = Field(min_length=1, max_length=2000)
+    confirm_label: str = Field(default="确认", min_length=1, max_length=40)
+
+
 class StartupConfig(CamelModel):
     execution_mode: Literal["sequential"] = "sequential"
     actions: list[StartupAction] = Field(default_factory=list, max_length=5)
+    opening_message: OpeningMessageConfig | None = None
 
     @model_validator(mode="after")
     def validate_unique_action_ids(self):
@@ -163,13 +172,17 @@ class AssistantUpsert(CamelModel):
                 setattr(self, field, "")
         if "graph" not in allowed:
             self.graph = {}
+        if self.type == "workflow":
+            self.greeting = ""
         if self.type not in {"prompt", "workflow"}:
             self.tool_ids = []
             self.dynamic_variable_definitions = {}
         if self.type != "prompt":
             self.startup = StartupConfig()
-        if self.runtime_mode == "realtime" and self.startup.actions:
-            raise ValueError("Prompt Realtime 模式暂不支持启动 Action")
+        if self.runtime_mode == "realtime" and (
+            self.startup.actions or self.startup.opening_message is not None
+        ):
+            raise ValueError("Prompt Realtime 模式暂不支持启动阶段")
         # 外部托管大脑只能 cascade,拦住不兼容的 realtime
         if self.runtime_mode == "realtime" and self.type not in REALTIME_CAPABLE_TYPES:
             raise ValueError(f"类型 {self.type} 不支持 realtime 运行模式")