feat(birmel): update bot username after election ends

Add updateBotUsername function to change the bot's global username
(not just nickname) to match the winning persona after an election.
Uses the same naming pattern as nicknames (e.g., "aaron" -> "Bvaron").

Author: claude

packages/birmel/src/elections/bot-profile.ts

@@ -1,5 +1,6 @@
 import { getDiscordClient } from "../discord/client.js";
 import { getDiscordIdForPersona } from "./persona-discord-ids.js";
+import { generateNickname } from "./winner.js";
 import { loggers } from "../utils/index.js";
 
 const logger = loggers.scheduler.child("elections").child("profile");
@@ -33,6 +34,9 @@ export async function updateBotProfile(personaName: string): Promise<void> {
 		// Fetch and update bio using REST API
 		await updateBotBio(discordId);
 
+		// Update bot username to match persona
+		await updateBotUsername(personaName);
+
 		logger.info("Bot profile updated to match winner", {
 			personaName,
 			discordId,
@@ -84,3 +88,22 @@ async function updateBotBio(winnerDiscordId: string): Promise<void> {
 		// Bio update failure is not critical, continue without throwing
 	}
 }
+
+async function updateBotUsername(personaName: string): Promise<void> {
+	const client = getDiscordClient();
+	if (!client.user) return;
+
+	try {
+		// Generate username using the same pattern as nickname (e.g., "aaron" -> "Bvaron")
+		const username = generateNickname(personaName);
+
+		// Update the bot's username using REST API
+		await client.rest.patch("/users/@me", {
+			body: { username },
+		});
+		logger.info("Bot username updated", { personaName, username });
+	} catch (error) {
+		logger.error("Failed to update bot username", error, { personaName });
+		// Username update failure is not critical, continue without throwing
+	}
+}