feat: distill any oversized goal objective, not just plans

The distillation moved from PlanView into setSessionGoal — the shared
choke point for every goal source (composer, fork dialog, plans) — and
into the scheduled-tasks goal creation server-side. Any objective over
5000 chars is distilled into completion criteria by the small model; on a
transient failure a head+tail excerpt keeps the intent (top) and the
acceptance criteria (bottom) with a trim marker, plus a toast. The
working agent always received the full prompt in chat — only the auditor
is bound by the limit.

packages/ui/src/lib/i18n/messages/ko.ts

@@ -1439,7 +1439,7 @@ export const dict: Record<I18nKey, string> = {
   'chat.goal.action.save': '목표 저장',
   'chat.goal.action.start': '목표 시작',
   'chat.goal.toast.actionFailed': '목표 업데이트에 실패했습니다',
-  'plans.goal.toast.distillFallback': '감사용으로 계획을 요약하지 못했습니다 — 발췌본을 사용합니다',
+  'chat.goal.toast.distillFallback': '목표가 제한을 초과했고 요약도 실패했습니다 — 감사에는 발췌본을 사용합니다',
   'chat.goal.row.aria': '세션 목표 — 세부 정보 열기',
   'chat.goal.button.createAria': '세션 목표 설정',
   'chat.goal.button.manageAria': '세션 목표 관리',