feat: jev 接入，判断创建、修改、问答、不明确四类意图

app/schemas/screen.py

@@ -0,0 +1,48 @@
+"""大屏公共结构；组件属性、事件与数据源配置保持开放"""
+
+from typing import Annotated, Self
+
+from pydantic import Field, model_validator
+
+from .base import ExtensibleModel, JsonObject, NonBlankString
+
+Number = int | float
+PositiveNumber = Annotated[Number, Field(gt=0)]
+
+
+class Canvas(ExtensibleModel):
+    width: PositiveNumber
+    height: PositiveNumber
+
+
+class Layout(ExtensibleModel):
+    x: Number
+    y: Number
+    width: PositiveNumber
+    height: PositiveNumber
+
+
+class ScreenNode(ExtensibleModel):
+    id: NonBlankString
+    type: NonBlankString
+    layout: Layout
+    name: str | None = None
+    props: JsonObject = Field(default_factory=dict)
+    style: JsonObject | None = None
+    events: list[JsonObject] | None = None
+
+
+class Screen(ExtensibleModel):
+    canvas: Canvas
+    nodes: list[ScreenNode]
+    # 保持前端字段名；数据源的具体类型与绑定校验后续再引入
+    dataSource: list[JsonObject] = Field(default_factory=list)
+
+    @model_validator(mode="after")
+    def unique_node_ids(self) -> Self:
+        seen: set[str] = set()
+        for node in self.nodes:
+            if node.id in seen:
+                raise ValueError(f"重复的节点 ID: {node.id}")
+            seen.add(node.id)
+        return self