fix(input): correct lon mapping

internal/engine/events.go

@@ -26,10 +26,13 @@ type EventSummary struct {
 }
 
 // EventSink collects events from models and the integrator, aggregating
-// duplicate types into a single EventSummary. Safe for concurrent use.
+// duplicate types into a single EventSummary. It also carries the run's first
+// unrecoverable failure, which is a different thing from an event — see Fail.
+// Safe for concurrent use.
 type EventSink struct {
 	mu        sync.Mutex
 	summaries map[string]*EventSummary
+	err       error
 }
 
 // NewEventSink returns an empty sink.
@@ -61,6 +64,42 @@ func (s *EventSink) Emit(typ string, t float64, state State, message string) {
 	}
 }
 
+// Fail records the run's first unrecoverable error. Nil-safe, like Emit.
+//
+// Deliberately not an event. An event is an observation the caller may choose to
+// ignore: "above_model" means samples above the highest pressure level were
+// extrapolated, which degrades the answer without invalidating it. A failure
+// means the sampler had no data at all, so the trajectory from that point on is
+// not a forecast and must not be returned as one.
+//
+// Routing both through Emit is how the second came to be treated like the first.
+// WindTransport discarded the sampler's error and returned a zero rate, which is
+// indistinguishable from calm air, so any launch past the dataset's horizon
+// integrated with no wind and produced a balloon that took off and landed on the
+// same spot — reported as a successful prediction.
+//
+// Only the first failure is kept: it is the one that explains the run.
+func (s *EventSink) Fail(err error) {
+	if s == nil || err == nil {
+		return
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.err == nil {
+		s.err = err
+	}
+}
+
+// Err returns the first failure passed to Fail, or nil if the run was sound.
+func (s *EventSink) Err() error {
+	if s == nil {
+		return nil
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.err
+}
+
 // Snapshot returns a stable copy of every summary in deterministic order
 // (sorted by Type).
 func (s *EventSink) Snapshot() []EventSummary {