feat: show speaker nickname instead of raw user ID in voice logs

Resolve the Discord user ID to a server nickname / global name (cached) and
display that in the transcript channel + console logs.

bot/src/userbot.ts

@@ -38,6 +38,9 @@ export interface TurnInfo {
   /** Discord user ID of the speaker, so the transcript shows whose audio
    *  produced each turn (and which user a dropped/VAD turn belongs to). */
   user?: string;
+  /** Resolved display name (server nickname / global name); shown instead of
+   *  the raw user ID when available. */
+  userName?: string;
   transcript: string;
   reply: string;
   note?: string;
@@ -72,7 +75,7 @@ function durSec(a?: number, b?: number): string | null {
  *  timing breakdown (listening / LLM / TTS) with start→end wall-clock times and
  *  durations, so it's obvious what took long. Pure + exported for testing. */
 export function formatTurnMessage(info: TurnInfo): string {
-  const who = info.user ? `👤 ${info.user}  ` : "";
+  const who = info.userName || info.user ? `👤 ${info.userName || info.user}  ` : "";
   const head = info.transcript
     ? `${who}🎤 들음 → 🗣️ "${info.transcript}"\n🤖 답변: ${(info.reply || "").trim() || "(무응답)"}`
     : `${who}🎤 들음 → ❌ ${info.note || "무시됨"}`;
@@ -124,7 +127,7 @@ async function joinAndListen(client: AnyClient, channelId: string): Promise<void
   // joinVoiceChannel (it exposes id, guild.id and guild.voiceAdapterCreator).
   const session = await joinChannel(channel as unknown as VoiceBasedChannel);
   session.onTurn = (info) => {
-    console.log(`👤 ${info.user || "?"} 🗣️  ${info.transcript || "(" + (info.note || "empty") + ")"}\n🤖 ${info.reply}`);
+    console.log(`👤 ${info.userName || info.user || "?"} 🗣️  ${info.transcript || "(" + (info.note || "empty") + ")"}\n🤖 ${info.reply}`);
     // Mirror every heard utterance (and the reply / drop reason) to a text
     // channel so you can see what the bot understood even when it doesn't answer.
     void postTranscript(client, info);

bot/src/voice.ts

@@ -81,6 +81,9 @@ export class VoiceSession {
    *  diagnosable. `note` says why (e.g. "음성 아님(VAD 차단)", "너무 짧음", "ok"). */
   onTurn?: (info: {
     user: string;
+    /** Resolved display name (server nickname / global name) for the speaker,
+     *  so logs show a human name instead of the raw Discord user ID. */
+    userName?: string;
     transcript: string;
     reply: string;
     note?: string;
@@ -164,6 +167,31 @@ export class VoiceSession {
     });
   }
 
+  /** Resolve a speaker's Discord user ID to a human display name (server
+   *  nickname, else global name / username), cached so we don't refetch every
+   *  utterance. Falls back to the ID if lookup fails. */
+  private nameCache = new Map<string, string>();
+  private async displayName(userId: string): Promise<string> {
+    const cached = this.nameCache.get(userId);
+    if (cached) return cached;
+    let name = userId;
+    try {
+      const guild: any = this.client?.guilds?.cache?.get(this.guildId);
+      let member: any = guild?.members?.cache?.get(userId);
+      if (!member && guild?.members?.fetch) member = await guild.members.fetch(userId).catch(() => null);
+      if (member) {
+        name = member.displayName || member.nickname || member.user?.globalName || member.user?.username || userId;
+      } else {
+        const u: any = this.client?.users?.cache?.get(userId) || (await this.client?.users?.fetch?.(userId).catch(() => null));
+        name = u?.globalName || u?.username || userId;
+      }
+    } catch {
+      /* fall back to id */
+    }
+    this.nameCache.set(userId, name);
+    return name;
+  }
+
   private async captureUtterance(userId: string): Promise<void> {
     // Don't start a new capture once we're tearing down (user left).
     if (this.destroyed) return;
@@ -199,6 +227,7 @@ export class VoiceSession {
     if (mono.length < DISCORD_RATE * 0.3 * 2) {
       this.onTurn?.({
         user: userId,
+        userName: await this.displayName(userId),
         transcript: "",
         reply: "",
         note: "너무 짧음(<300ms)",
@@ -247,6 +276,7 @@ export class VoiceSession {
       // explains why a turn did or didn't answer, with full stage timing.
       this.onTurn?.({
         user: userId,
+        userName: await this.displayName(userId),
         transcript: metaSeen?.transcript ?? "",
         reply: metaSeen?.reply ?? "",
         note: metaSeen?.note,