fix(i18n): complete command center texts and merge client fallbacks

src/i18n/merge-messages.ts

@@ -0,0 +1,17 @@
+export type MessageTree = { [key: string]: string | MessageTree };
+
+/** Fill missing translations before sending messages to server and client consumers. */
+export function mergeMessages(
+	fallback: MessageTree,
+	localized: MessageTree,
+): MessageTree {
+	const result: MessageTree = { ...fallback };
+	for (const [key, value] of Object.entries(localized)) {
+		const base = fallback[key];
+		result[key] =
+			typeof value === "object" && typeof base === "object"
+				? mergeMessages(base, value)
+				: value;
+	}
+	return result;
+}