story-kit: merge 227_bug_thinking_traces_visible_in_agents_panel_in_release_builds_only

frontend/src/components/AgentPanel.tsx

@@ -175,6 +175,9 @@ export function AgentPanel({
 									terminalAt: current.terminalAt ?? Date.now(),
 								},
 							};
+						case "thinking":
+							// Thinking traces are internal model state — never display them.
+							return prev;
 						default:
 							return prev;
 					}