perf: skip deep clone per streaming token in ResponseMessage

Author: Algorithm5838

src/lib/components/chat/Chat.svelte

@@ -619,11 +619,7 @@
 				const data = event?.data?.data ?? null;
 
 				if (type === 'status') {
-					if (message?.statusHistory) {
-						message.statusHistory.push(data);
-					} else {
-						message.statusHistory = [data];
-					}
+					message.statusHistory = [...(message?.statusHistory ?? []), data];
 				} else if (type === 'context_compaction') {
 					handleContextCompactionStatus(data);
 				} else if (type === 'chat:active') {

src/lib/components/chat/Messages/ResponseMessage.svelte

@@ -134,7 +134,13 @@
 				message.done !== source.done ||
 				message.output?.length !== source.output?.length
 			) {
-				message = structuredClone(source);
+				if (!message.done && source.done) {
+					// done just flipped: full clone to snapshot final state (info, usage, etc.)
+					message = structuredClone(source);
+				} else {
+					// mid-stream: shallow copy keeps all fields fresh without deep recursion
+					message = { ...source };
+				}
 			} else if (!equal(message, source)) {
 				// Slow path: full comparison for infrequent changes (sources, annotations, status, etc.)
 				message = structuredClone(source);