Move settings into a standalone Settings window

The tab-bar popover had outgrown itself. Settings now open in their own
native window (a fourth window kind, built like the connection manager but
not modal): a sidebar with Appearance, Transfers, Editor, File list and
About, holding every popover row plus the visible-columns choice. Each
control is an ordinary settings save, so the other windows follow live
while it stays open.

The gear button in the tab bar, Ctrl+, and the macOS app menu's
"Settings..." (Cmd+,) open it. On macOS Cmd+W arrives as the main window's
close-tab menu action, so bun closes the focused Settings window first
instead of a main-window tab.

Co-Authored-By: Claude <noreply@anthropic.com>

src/shared/i18n/ja.ts

@@ -24,14 +24,22 @@ export const ja = {
 		manageConnections: "接続を管理",
 		newTab: "新しいタブ ({mod}T)",
 		closeTab: "タブを閉じる ({mod}W)",
-		options: "オプション",
+		options: "設定",
 		update: "アップデートあり",
 		updating: "更新中",
 		restartToUpdate: "再起動して適用",
 		updateTooltip: "アップデートがあります: miniSCP {version}",
 	},
 	options: {
-		title: "オプション",
+		title: "設定",
+		sections: {
+			appearance: "外観",
+			transfers: "転送",
+			editor: "エディタ",
+			fileList: "ファイル一覧",
+			about: "情報",
+		},
+		columns: "表示する列",
 		language: "言語",
 		system: "システム",
 		theme: { label: "テーマ", system: "システム", light: "ライト", dark: "ダーク" },
@@ -248,6 +256,7 @@ export const ja = {
 	},
 	menu: {
 		about: "{app} について",
+		settings: "設定…",
 		checkForUpdates: "アップデートを確認…",
 		quit: "終了",
 		file: "ファイル",