perf: O(1) field checks in ResponseMessage slow path

Author: Algorithm5838

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

@@ -132,8 +132,20 @@
 				} else {
 					message = { ...message, content: source.content, done: source.done };
 				}
-			} else if (JSON.stringify(message) !== JSON.stringify(source)) {
-				// Slow path: full comparison for infrequent changes (sources, annotations, status, etc.)
+			} else if (
+				message.statusHistory?.length  !== source.statusHistory?.length  ||
+				message.sources?.length        !== source.sources?.length        ||
+				message.annotation             !== source.annotation             ||
+				message.followUps              !== source.followUps              ||
+				message.error                  !== source.error                  ||
+				message.files                  !== source.files                  ||
+				message.embeds                 !== source.embeds                 ||
+				message.favorite               !== source.favorite               ||
+				JSON.stringify(message.code_executions) !== JSON.stringify(source.code_executions)
+			) {
+				// Slow path: O(1) field checks for infrequent post-streaming mutations.
+				// Push-mutated arrays use length; assigned fields use reference inequality;
+				// code_executions uses JSON.stringify since entries can be replaced at a fixed index.
 				message = structuredClone(source);
 			}
 		}