fix(web): name the subagent-session refusal in the schedule editor

`subagent_session` joins the update-result error union, so the client's
exhaustive mapping needs an entry: the timing switch returns a new
`timing.subagentSession` key and both locale dictionaries carry the copy.
The editor shows it when someone edits a task whose Session subagent routing
owns.

packages/client/ui-schedule/src/client/task-manager-locales.ts

@@ -84,6 +84,7 @@ export const en = {
   'timing.conflict': 'This task changed while you were editing. Your draft is retained. '
     + 'Cancel and reopen after refresh to edit the latest rule.',
   'timing.notFound': 'This task is no longer available. Your draft is retained; cancel to close the editor.',
+  'timing.subagentSession': 'This session belongs to a sub-agent, which never receives delivered reminders.',
   'timing.invalid': 'Enter a valid date and time, or check the timing fields.',
   'timing.invalidZone': 'Enter a valid IANA time zone, for example Asia/Shanghai.',
   'timing.notFuture': 'Choose a date and time in the future.',
@@ -226,6 +227,7 @@ export const zh: Record<TaskManagerKey, string> = {
   'timing.inactive': '已结束的任务为只读，无法修改时间',
   'timing.conflict': '编辑期间任务已变化，草稿已保留。请在刷新后取消并重新打开编辑器，以修改最新规则',
   'timing.notFound': '此任务当前不可用，草稿已保留。请取消以关闭编辑器',
+  'timing.subagentSession': '此会话属于子 agent，永远不会收到投递的提醒',
   'timing.invalid': '请输入有效的日期和时间，或检查时间字段',
   'timing.invalidZone': '请输入有效的 IANA 时区，例如 Asia/Shanghai',
   'timing.notFuture': '请选择未来的日期和时间',

packages/client/ui-schedule/src/client/task-timing.ts

@@ -189,6 +189,7 @@ export function timingError(code: Extract<ScheduleUpdateResult, { code: string }
     case 'schedule_conflict': return 'timing.conflict'
     case 'schedule_ended': return 'timing.inactive'
     case 'schedule_not_found': return 'timing.notFound'
+    case 'subagent_session': return 'timing.subagentSession'
     case 'invalid_time_zone': return 'timing.invalidZone'
     case 'not_future': return 'timing.notFuture'
     case 'frequency_too_high': return 'timing.invalidInterval'