chore: import upstream snapshot with attribution

apps/webapp/app/v3/eventRepository/emergencySpanCap.server.ts

@@ -0,0 +1,8 @@
+import { env } from "~/env.server";
+
+// Emergency circuit breaker for trace views: when TRACE_VIEW_EMERGENCY_SPAN_CAP
+// is set, clamp a trace summary span limit to it. Unset = no clamping.
+export function clampToEmergencySpanCap(limit: number): number {
+  const cap = env.TRACE_VIEW_EMERGENCY_SPAN_CAP;
+  return cap === undefined ? limit : Math.min(limit, cap);
+}