feat: add window execution to runtime

crates/crank-runtime/src/streaming.rs

@@ -0,0 +1,13 @@
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+#[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+pub struct WindowExecutionResult {
+    pub summary: Value,
+    pub items: Vec<Value>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub cursor: Option<Value>,
+    pub window_complete: bool,
+    pub truncated: bool,
+    pub has_more: bool,
+}