feat: surface session goal evaluation model and add diagnostics

Shows the evaluation provider/model used for the latest successful goal audit in the UI.
Persists evaluation model metadata on session goals and covers it in tests.
Adds diagnostic logging for small-model calls and session-goal audit parsing.

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

@@ -1418,6 +1418,7 @@ export const dict: Record<I18nKey, string> = {
   'chat.goal.dialog.objectiveLabel': '목표',
   'chat.goal.dialog.objectivePlaceholder': '에이전트가 도달하고 검증해야 할 최종 상태를 설명하세요…',
   'chat.goal.dialog.budgetLabel': '토큰 예산',
+  'chat.goal.dialog.evaluationModelLabel': '평가 모델',
   'chat.goal.status.active': '진행 중',
   'chat.goal.status.evaluating': '평가 중…',
   'chat.goal.status.paused': '일시 중지됨',