Make "Show original" in the headers dialog the action, not a description

The hint at the foot of Message headers named an action and left you to go
find it. Requested in #236, and the reporter is right that it is the shape of
the thing rather than the size: telling somebody a feature exists is half a
job when the other half is one element away.

Clicking it now closes the headers dialog and opens the original, so it reads
as going deeper rather than as opening a second window.

`tNode` rather than a sentence chopped either side of a button: the sentence
stays whole for whoever translates it, and a language that puts the verb
somewhere else can move the hole rather than being handed two fragments.

The link style needed unscoping to work, which turned out to be a bug of its
own. `.link-btn` was written for the composer's To and Cc labels and scoped to
`.composer-field label`, so the two callers outside it -- the trusted-domain
list in Privacy settings, and now this -- rendered as default button chrome in
the middle of a sentence. The rule is now unscoped and Privacy is fixed by the
same change.

Checked in a browser: the hint reads as a sentence with a dotted-underlined
link in it, clicking swaps one dialog for the other, and the raw message is
there.

Closes #236.

web/src/locales/de.ts

@@ -225,7 +225,7 @@ export const catalog: Catalog = {
     "Never send one": "Nie senden",
     "Not this time": "Diesmal nicht",
     "It would go to {address}, which is not where the message came from.": "Sie ginge an {address} — nicht dorthin, woher die Nachricht kam.",
-    "Use “Show original” for the complete raw message.": "Nutzen Sie „Original anzeigen“ für die vollständige Rohnachricht.",
+    "Use {action} for the complete raw message.": "{action} für die vollständige Rohnachricht.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Ordner",

web/src/locales/es.ts

@@ -217,7 +217,7 @@ export const catalog: Catalog = {
     "Never send one": "No enviar nunca",
     "Not this time": "Esta vez no",
     "It would go to {address}, which is not where the message came from.": "Iría a {address}, que no es de donde vino el mensaje.",
-    "Use “Show original” for the complete raw message.": "Use «Mostrar el original» para ver el mensaje sin procesar completo.",
+    "Use {action} for the complete raw message.": "{action} para ver el mensaje sin procesar completo.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Carpeta",

web/src/locales/fr.ts

@@ -222,7 +222,7 @@ export const catalog: Catalog = {
     "Never send one": "Ne jamais en envoyer",
     "Not this time": "Pas cette fois",
     "It would go to {address}, which is not where the message came from.": "Il irait à {address}, qui n'est pas l'origine du message.",
-    "Use “Show original” for the complete raw message.": "Utilisez « Afficher l'original » pour le message brut complet.",
+    "Use {action} for the complete raw message.": "{action} pour le message brut complet.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Dossier",

web/src/locales/ja.ts

@@ -216,7 +216,7 @@ export const catalog: Catalog = {
     "Never send one": "送信しない",
     "Not this time": "今回は送信しない",
     "It would go to {address}, which is not where the message came from.": "送信先は {address} で、メールの送信元とは異なります。",
-    "Use “Show original” for the complete raw message.": "完全な原文は「元のメールを表示」でご覧いただけます。",
+    "Use {action} for the complete raw message.": "完全な生メッセージは {action} から。",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "フォルダー",

web/src/locales/nl.ts

@@ -213,7 +213,7 @@ export const catalog: Catalog = {
     "Never send one": "Nooit versturen",
     "Not this time": "Deze keer niet",
     "It would go to {address}, which is not where the message came from.": "Die zou naar {address} gaan, en daar kwam het bericht niet vandaan.",
-    "Use “Show original” for the complete raw message.": "Gebruik “Origineel tonen” voor het volledige ruwe bericht.",
+    "Use {action} for the complete raw message.": "{action} voor het volledige onbewerkte bericht.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Map",

web/src/locales/pt-BR.ts

@@ -220,7 +220,7 @@ export const catalog: Catalog = {
     "Never send one": "Nunca enviar",
     "Not this time": "Desta vez não",
     "It would go to {address}, which is not where the message came from.": "Ela iria para {address}, que não é de onde a mensagem veio.",
-    "Use “Show original” for the complete raw message.": "Use “Mostrar o original” para ver a mensagem bruta completa.",
+    "Use {action} for the complete raw message.": "{action} para a mensagem bruta completa.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Pasta",

web/src/locales/ru.ts

@@ -219,7 +219,7 @@ export const catalog: Catalog = {
     "Never send one": "Никогда не отправлять",
     "Not this time": "Не в этот раз",
     "It would go to {address}, which is not where the message came from.": "Оно ушло бы на {address}, а письмо пришло не оттуда.",
-    "Use “Show original” for the complete raw message.": "Нажмите «Показать исходник», чтобы увидеть письмо целиком.",
+    "Use {action} for the complete raw message.": "{action} — полное исходное сообщение.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Папка",

web/src/locales/uk.ts

@@ -213,7 +213,7 @@ export const catalog: Catalog = {
     "Never send one": "Ніколи не надсилати",
     "Not this time": "Не цього разу",
     "It would go to {address}, which is not where the message came from.": "Воно пішло б на {address}, а лист надійшов не звідти.",
-    "Use “Show original” for the complete raw message.": "Натисніть «Показати оригінал», щоб побачити лист повністю.",
+    "Use {action} for the complete raw message.": "{action} — повне вихідне повідомлення.",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "Тека",

web/src/locales/zh-Hans.ts

@@ -215,7 +215,7 @@ export const catalog: Catalog = {
     "Never send one": "从不发送",
     "Not this time": "这次不发送",
     "It would go to {address}, which is not where the message came from.": "回执会发往 {address}，而邮件并非来自该地址。",
-    "Use “Show original” for the complete raw message.": "使用「显示原始邮件」查看完整原文。",
+    "Use {action} for the complete raw message.": "{action} 可查看完整原始邮件。",
 
     // ── Folders, calendar, contacts, files ─────────────────────────────
     "Folder": "文件夹",