fix(workbench): keep projected trace times monotonic (#2054)

internal/cloud/workbench-projection-writer.ts

@@ -110,13 +110,14 @@ export async function writeWorkbenchProjectionEvent({ runtimeStore = null, event
   if (!traceId) return null;
   const projectedAt = new Date().toISOString();
   const sourceSeq = nonNegativeInteger(event.sourceSeq ?? event.seq);
-  const occurredAt = timestampValue(event.createdAt ?? event.occurredAt ?? event.updatedAt ?? projectedAt);
   const sessionId = textValue(event.sessionId ?? requestMeta.sessionId) || null;
   const turnId = textValue(event.turnId) || traceId;
   const terminal = event.terminal === true || TERMINAL_STATUSES.has(normalizeWorkbenchStatus(event.status));
   const status = terminal ? normalizeWorkbenchStatus(event.status) : "running";
   const previousCheckpoint = await latestWorkbenchCheckpoint(runtimeStore, traceId);
   const previousTiming = normalizeTimingProjection(previousCheckpoint?.timing) ?? normalizeTimingProjection(previousCheckpoint);
+  const sourceOccurredAt = timestampValue(event.createdAt ?? event.occurredAt ?? event.updatedAt ?? projectedAt);
+  const occurredAt = latestTimestamp(previousTiming?.lastEventAt, sourceOccurredAt) ?? sourceOccurredAt;
   const previousTerminal = checkpointIsTerminal(previousCheckpoint);
   const suppressedAfterSeal = previousTerminal && !terminal;
   const explicitEventTiming = normalizeTimingProjection(event.timing) ?? normalizeTimingProjection(event);
@@ -222,6 +223,8 @@ export async function writeWorkbenchProjectionEvent({ runtimeStore = null, event
       finishedAt: eventTiming?.finishedAt ?? null,
       durationMs: eventTiming?.durationMs ?? null,
       suppressedAfterSeal,
+      sourceOccurredAt: sourceOccurredAt !== occurredAt ? sourceOccurredAt : null,
+      createdAt: occurredAt,
       occurredAt,
       updatedAt: projectedAt
     }],