fix(workbench): derive running timing from trace events (#1981)

Co-authored-by: root <root@lyon.remote>

internal/cloud/server-workbench-http.ts

@@ -884,7 +884,7 @@ function factTraceSnapshot(facts = {}, traceId) {
   const status = durableTraceStatus(events);
   const lastEvent = events.at(-1) ?? null;
   const checkpoint = factCheckpointForTrace(facts, safeTrace);
-  const timing = factTimingProjection(checkpoint, status);
+  const timing = factTraceTimingProjection(events, checkpoint, status);
   return {
     traceId: safeTrace,
     status,
@@ -902,6 +902,29 @@ function factTraceSnapshot(facts = {}, traceId) {
   };
 }
 
+function factTraceTimingProjection(events = [], checkpoint = null, status = null) {
+  const checkpointTiming = factTimingProjection(checkpoint, status);
+  const normalizedStatus = normalizeStatus(status ?? checkpoint?.status);
+  const terminal = TERMINAL_STATUSES.has(normalizedStatus) && !RUNNING_STATUSES.has(normalizedStatus);
+  const observedAt = new Date().toISOString();
+  const eventTimes = factArray(events).flatMap((event) => [event?.createdAt, event?.updatedAt, event?.occurredAt]);
+  const startedAt = firstTimestampIso(checkpointTiming.startedAt, ...eventTimes);
+  const lastEventAt = latestTimestampIso(checkpointTiming.lastEventAt, ...eventTimes);
+  const finishedAt = terminal ? latestTimestampIso(checkpointTiming.finishedAt, lastEventAt) : null;
+  const durationMs = elapsedFactMs(startedAt, terminal ? finishedAt : observedAt);
+  const lastEventAgeMs = terminal ? null : elapsedFactMs(lastEventAt, observedAt);
+  return {
+    ...checkpointTiming,
+    startedAt,
+    lastEventAt,
+    finishedAt,
+    durationMs,
+    observedAt: terminal ? null : observedAt,
+    lastEventAgeMs,
+    valuesRedacted: true
+  };
+}
+
 function factTraceEventDto(event, index) {
   const seq = factProjectedSeq(event);
   if (!seq) return null;