fix(walkthrough): stop the importance tag reading as a review finding

The "Critical" pill was painted in the status-error colour, so a stop marked
because it drives the change read as a severity reported against the code —
the one thing this feature never does. It is now "Key change", carries its
emphasis with weight and an outline rather than a status colour, and both tags
state their meaning in a tooltip. The panel links the guide from its header,
and the guide gained a section on what the tags mean and what they do not.

Also corrects two German strings that translated the noun "stop" as the verb.

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

@@ -1144,8 +1144,11 @@ export const dict: Record<I18nKey, string> = {
   'walkthrough.toc.moreFiles': '다른 파일: {count}',
   'walkthrough.toc.uncovered': '미포함: {count}',
   'walkthrough.toc.resize': '목차 열 너비 조절',
-  'walkthrough.importance.critical': '중요',
+  'walkthrough.importance.critical': '핵심 변경',
+  'walkthrough.importance.criticalHint': '이 단계가 변경 전체를 이끌고 있으니 꼼꼼히 읽어 보세요. 코드에서 발견된 문제가 아닙니다.',
   'walkthrough.importance.context': '참고',
+  'walkthrough.importance.contextHint': '나머지를 이해하는 데 도움이 되도록 함께 실은 보조 변경입니다.',
+  'walkthrough.help.guide': '워크스루 작동 방식',
   'walkthrough.blocked.noModel.title': '사용할 수 있는 스몰 모델이 없습니다',
   'walkthrough.blocked.noModel.description': '리뷰를 생성하려면 모델 제공자에 로그인하세요.',
   'walkthrough.blocked.emptyDiff.title': '리뷰할 내용이 없습니다',