Merge pull request #1773 from pikasTech/fix/1770-turn-timing-authority

fix: keep turn timing independent from sessions

internal/cloud/workbench-turn-projection.ts

@@ -48,7 +48,10 @@ export function createWorkbenchTurnTimingProjection({ result = null, session = n
   const firstEvent = events[0] ?? null;
   const lastEvent = traceLastEvent(trace);
   const terminalEvent = terminalTraceEventForTiming(events);
-  const directTiming = objectValue(result?.timing) ?? objectValue(trace?.timing) ?? objectValue(session?.timing) ?? null;
+  // Session lifecycle timing is not turn timing authority. Mixing session
+  // startedAt/createdAt with turn terminal duration makes the running timer
+  // jump backwards when the turn completes.
+  const directTiming = objectValue(result?.timing) ?? objectValue(trace?.timing) ?? null;
   const agentRun = objectValue(result?.agentRun ?? trace?.agentRun);
   const traceSummary = objectValue(result?.traceSummary ?? trace?.traceSummary);
   const sessionSnapshot = objectValue(session?.session);
@@ -63,11 +66,7 @@ export function createWorkbenchTurnTimingProjection({ result = null, session = n
     agentRun?.startedAt,
     firstEvent?.startedAt,
     firstEvent?.createdAt,
-    firstEvent?.occurredAt,
-    session?.startedAt,
-    session?.createdAt,
-    sessionSnapshot?.startedAt,
-    sessionSnapshot?.createdAt
+    firstEvent?.occurredAt
   );
   const lastEventAt = firstTimestamp(
     result?.lastEventAt,