fix(session): retain fork tail until the first inbox change

packages/api/session-controller/src/commands.ts

@@ -240,7 +240,12 @@ export class SessionCommandController {
         { sessionId: request.sessionId },
       )
     }
-    const cut = SessionLogOffset(boundary.seq + 1)
+    let cut = SessionLogOffset(boundary.seq + 1)
+    while (cut < source.events.length
+      && source.events[cut]?.type !== 'turn/start'
+      && source.events[cut]?.type !== 'agent/inbox/spliced') {
+      cut = SessionLogOffset(cut + 1)
+    }
     let workspace: Workspace | undefined
     try {
       workspace = await this.forkWorkspace(source.header)