fix(session-title): preserve agent turn outcomes

packages/core/session/src/index.ts

@@ -27,6 +27,27 @@ export type { SessionSurface, SurfaceFoldReplacement, SurfaceFoldResult } from '
 export { foldSurface, isSurfaceEvent, isSurfaceEligibleType } from './surface.ts'
 export { canonicalHeader, foldRequestHeader, headerEquals } from './request-header.ts'
 
+/**
+ * Find the latest closed message-triggered turn, excluding injection and
+ * plugin-owned zero-step turns.
+ * @param events - session events, or an owned suffix, to inspect.
+ * @returns the latest matching turn end, or `undefined`.
+ */
+export function findLastMessageTurnEnd(
+  events: readonly SessionEvent[],
+): SessionEvent<'turn/end'> | undefined {
+  const messageTurns = new Set<number>()
+  let latest: SessionEvent<'turn/end'> | undefined
+  for (const event of events) {
+    if (event.type === 'turn/start') {
+      if (event.data.trigger.kind === 'message') messageTurns.add(event.data.turn)
+      continue
+    }
+    if (event.type === 'turn/end' && messageTurns.delete(event.data.turn)) latest = event
+  }
+  return latest
+}
+
 declare module 'cordis' {
   interface Context {
     sessions: SessionStore