feat: improved agent streaming

surfsense_web/components/assistant-ui/step-separator.tsx

@@ -0,0 +1,27 @@
+"use client";
+
+import { makeAssistantDataUI } from "@assistant-ui/react";
+
+/**
+ * Renders a thin horizontal divider between model steps within a single
+ * assistant turn. The data part is pushed by `addStepSeparator` in
+ * `streaming-state.ts` whenever a `start-step` SSE event arrives after
+ * the message already has non-step content.
+ *
+ * Today the backend emits one `start-step` / `finish-step` pair per turn,
+ * so most messages won't contain a separator. The renderer is wired up so
+ * the planned per-model-step refactor (A2 follow-up) can light up without
+ * touching the persistence path.
+ */
+function StepSeparatorDataRenderer() {
+	return (
+		<div className="mx-auto my-3 w-full max-w-(--thread-max-width) px-2">
+			<div className="border-t border-border/60" />
+		</div>
+	);
+}
+
+export const StepSeparatorDataUI = makeAssistantDataUI({
+	name: "step-separator",
+	render: StepSeparatorDataRenderer,
+});