improvement(mothership): treat error as terminal event (#4290)

Author: icecrasher321

apps/sim/lib/copilot/request/go/stream.ts

@@ -571,14 +571,14 @@ function stampSseReadLoopSpan(
   const nowWall = Date.now()
   const startWall = nowWall - (nowPerf - startPerfMs)
 
-  const terminalEventSeen = counters.eventsByType.complete > 0
+  const terminalEventSeen = counters.eventsByType.complete > 0 || counters.eventsByType.error > 0
   // `terminal_event_missing` is the single-attribute dashboard signal
   // for the "disappeared response" bug class: the caller considered
   // this leg to be the final one (`context.streamComplete === true`)
-  // but no `complete` event arrived on the wire. Tool-pause legs have
-  // expectedTerminal=false and never trip this, so dashboards can
-  // filter on `{ .copilot.sse.terminal_event_missing = true }` without
-  // false positives.
+  // but no terminal `complete` or `error` event arrived on the wire.
+  // Tool-pause legs have expectedTerminal=false and never trip this, so
+  // dashboards can filter on `{ .copilot.sse.terminal_event_missing = true }`
+  // without false positives.
   const terminalEventMissing = opts.expectedTerminal && !terminalEventSeen
 
   const tracer = getCopilotTracer()