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/pt-BR.ts

@@ -1144,8 +1144,11 @@ export const dict: Record<I18nKey, string> = {
   "walkthrough.toc.moreFiles": "Mais arquivos: {count}",
   "walkthrough.toc.uncovered": "Sem cobertura: {count}",
   "walkthrough.toc.resize": "Redimensionar a coluna de conteúdo",
-  "walkthrough.importance.critical": "Crítico",
+  "walkthrough.importance.critical": "Mudança principal",
+  "walkthrough.importance.criticalHint": "Este passo conduz o restante da mudança, então leia com atenção. Não é um problema encontrado no seu código.",
   "walkthrough.importance.context": "Contexto",
+  "walkthrough.importance.contextHint": "Uma mudança de apoio, incluída para que o restante faça sentido.",
+  "walkthrough.help.guide": "Como funcionam os walkthroughs",
   "walkthrough.blocked.noModel.title": "Nenhum modelo pequeno disponível",
   "walkthrough.blocked.noModel.description": "Entre em um provedor de modelos para gerar uma revisão.",
   "walkthrough.blocked.emptyDiff.title": "Nada para revisar",