feat(sidebar): tooltip for the active-session indicator dot (#782)

The pulsing green dot next to a session row signals that the session
had activity in the last 10 minutes, but the meaning was undocumented.
Hovering it now shows a translated tooltip, and an aria-label exposes
the same text to screen readers.

Uses the existing shared Tooltip component (portal-positioned, so it
is not clipped by the sidebar overflow). Translation key added to all
eight sidebar locale files (en, de, it, ja, ko, ru, tr, zh-CN).

src/i18n/locales/de/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "Aus Favoriten entfernen",
     "editSessionName": "Sitzungsname manuell bearbeiten",
     "deleteSession": "Diese Sitzung dauerhaft löschen",
+    "activeSessionIndicator": "Kürzlich aktive Sitzung (letzte 10 Minuten)",
     "save": "Speichern",
     "cancel": "Abbrechen",
     "clearSearch": "Suche leeren",

src/i18n/locales/en/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "Remove from favorites",
     "editSessionName": "Manually edit session name",
     "deleteSession": "Delete this session permanently",
+    "activeSessionIndicator": "Recently active session (last 10 minutes)",
     "save": "Save",
     "cancel": "Cancel",
     "clearSearch": "Clear search",

src/i18n/locales/it/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "Rimuovi dai preferiti",
     "editSessionName": "Modifica manualmente il nome della sessione",
     "deleteSession": "Elimina questa sessione permanentemente",
+    "activeSessionIndicator": "Sessione attiva di recente (ultimi 10 minuti)",
     "save": "Salva",
     "cancel": "Annulla",
     "clearSearch": "Cancella ricerca",

src/i18n/locales/ja/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "お気に入りから削除",
     "editSessionName": "セッション名を手動で編集",
     "deleteSession": "このセッションを完全に削除",
+    "activeSessionIndicator": "最近アクティブなセッション（過去10分以内）",
     "save": "保存",
     "cancel": "キャンセル",
     "openCommandPalette": "コマンドパレットを開く"

src/i18n/locales/ko/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "즐겨찾기에서 제거",
     "editSessionName": "세션 이름 직접 편집",
     "deleteSession": "이 세션 영구 삭제",
+    "activeSessionIndicator": "최근 활성 세션 (지난 10분)",
     "save": "저장",
     "cancel": "취소",
     "openCommandPalette": "명령 팔레트 열기"

src/i18n/locales/ru/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "Удалить из избранного",
     "editSessionName": "Вручную редактировать имя сеанса",
     "deleteSession": "Удалить этот сеанс навсегда",
+    "activeSessionIndicator": "Недавно активный сеанс (последние 10 минут)",
     "save": "Сохранить",
     "cancel": "Отмена",
     "clearSearch": "Очистить поиск",

src/i18n/locales/tr/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "Favorilerden çıkar",
     "editSessionName": "Oturum adını elle düzenle",
     "deleteSession": "Bu oturumu kalıcı olarak sil",
+    "activeSessionIndicator": "Yakın zamanda etkin oturum (son 10 dakika)",
     "save": "Kaydet",
     "cancel": "İptal",
     "clearSearch": "Aramayı temizle",

src/i18n/locales/zh-CN/sidebar.json

@@ -45,6 +45,7 @@
     "removeFromFavorites": "从收藏移除",
     "editSessionName": "手动编辑会话名称",
     "deleteSession": "永久删除此会话",
+    "activeSessionIndicator": "最近活跃的会话（最近 10 分钟）",
     "save": "保存",
     "cancel": "取消",
     "clearSearch": "清除搜索",