补齐画布合并后2MiB校验

在生成完成态合并与元数据迁移后重新校验最终布局大小

新增合并结果超过2MiB时拒绝保存的边界测试

server-rs/crates/spacetime-module/src/editor_project_storage.rs

@@ -1549,6 +1549,7 @@ fn persist_editor_project_layout(
         input_layers_json,
         now,
     )?;
+    let layers_json = normalize_layout_json(layers_json)?;
 
     ctx.db.editor_canvas().canvas_id().delete(&canvas.canvas_id);
     ctx.db.editor_canvas().insert(EditorCanvas {
@@ -5021,6 +5022,50 @@ mod tests {
         assert_eq!(error, "图片画布图层布局过大");
     }
 
+    #[test]
+    fn editor_layout_rejects_merged_result_over_two_mib() {
+        let incoming = json!([{
+            "itemType": "generation-dialog",
+            "layerId": "generation-dialog:dialog-1",
+            "resourceId": "generation-dialog:dialog-1",
+            "padding": "x".repeat(EDITOR_PROJECT_MAX_LAYOUT_JSON_BYTES - 200),
+            "dialog": {
+                "id": "dialog-1",
+                "mode": "generate",
+                "status": "generating"
+            }
+        }]);
+        let current = json!([
+            {
+                "layerId": "layer-generated",
+                "resourceId": "resource-generated",
+                "title": "生成结果"
+            },
+            {
+                "itemType": "generation-dialog",
+                "layerId": "generation-dialog:dialog-1",
+                "resourceId": "generation-dialog:dialog-1",
+                "dialog": {
+                    "id": "dialog-1",
+                    "mode": "generate",
+                    "status": "idle",
+                    "generatedLayerId": "layer-generated"
+                }
+            }
+        ]);
+        let merged = merge_completed_canvas_generation_items(
+            current.to_string().as_str(),
+            incoming.to_string(),
+        )
+        .expect("merge itself should succeed");
+
+        assert!(merged.len() > EDITOR_PROJECT_MAX_LAYOUT_JSON_BYTES);
+        assert_eq!(
+            normalize_layout_json(merged).expect_err("final merged layout should fail"),
+            "图片画布图层布局过大"
+        );
+    }
+
     fn public_showcase_asset() -> EditorShowcaseAsset {
         let now = Timestamp::from_micros_since_unix_epoch(1_000_000);
         EditorShowcaseAsset {