Internationalization: 7 languages with live switching

Custom signal-based runtime (no i18n dependency): shared src/shared/i18n
dictionaries, ui I18nService.t() reactive by construction so language
switches live, and a backend i18n.ts for native menus + thrown errors.
Every user-facing string keyed across templates, toasts, dialogs, file
kinds, columns, macOS menu/context menus, and errors. Language picker in
Options (auto-detects OS locale, falls back to English); switching
relabels the webview and native chrome instantly. English/Spanish/French/
German fully drafted; Chinese/Japanese/Basque drafted, flagged for native
review. Docs updated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/bun/fs/registry.ts

@@ -1,3 +1,4 @@
+import { t } from "../i18n";
 import { LocalProvider } from "./local";
 import type { FileSystemProvider } from "./provider";
 
@@ -15,7 +16,7 @@ export class SessionRegistry {
 
 	get(sessionId: string): FileSystemProvider {
 		const provider = this.sessions.get(sessionId);
-		if (!provider) throw new Error(`Session "${sessionId}" is not connected`);
+		if (!provider) throw new Error(t("errors.sessionNotConnected", { id: sessionId }));
 		return provider;
 	}
 
@@ -27,7 +28,7 @@ export class SessionRegistry {
 
 	async remove(sessionId: string): Promise<void> {
 		if (sessionId === LOCAL_SESSION_ID)
-			throw new Error("The local session cannot be disconnected");
+			throw new Error(t("errors.localCannotDisconnect"));
 		const provider = this.sessions.get(sessionId);
 		if (!provider) return;
 		this.sessions.delete(sessionId);