feat(bot): userbot (selfbot) mode — voice conversation on one user account (stage 1)

A user account is the only kind Discord lets Go Live, so add a userbot run mode:
when DISCORD_BOT_TOKEN is absent but DISCORD_SELFBOT_TOKEN is set, the app runs
as a userbot instead of the normal slash-command bot.

Stage 1 (conversation): log in with discord.js-selfbot-v13, auto-join
DISCORD_VOICE_CHANNEL_ID on startup (or "!자비스 join" when unset), listen via the
selfbot VoiceReceiver (pcm), transcribe+reply through the bridge, and speak the
reply back with playAudio. Shared PCM/WAV helpers extracted to audio.ts.
run-bot.sh now starts in either userbot or normal mode. Go-Live broadcast +
broadcast-coupled routing land in stage 2 on the same voice connection.

ToS note: selfbots violate Discord ToS; burner account only.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

bot/src/index.ts

@@ -184,4 +184,21 @@ async function handleStatus(i: ChatInputCommandInteraction) {
   );
 }
 
-client.login(config.botToken);
+// Mode select: a USER account is the only kind Discord lets Go Live, so when
+// there's no normal-bot token but a selfbot token is present, run as a userbot
+// (voice + broadcast on one user account). Otherwise run the legacy normal bot.
+(async () => {
+  if (!config.botToken && config.selfbotToken) {
+    const { runUserbot } = await import("./userbot.ts");
+    await runUserbot();
+  } else if (config.botToken) {
+    await client.login(config.botToken);
+  } else {
+    throw new Error(
+      "DISCORD_BOT_TOKEN(일반 봇) 또는 DISCORD_SELFBOT_TOKEN(유저봇) 중 하나는 .env에 필요합니다.",
+    );
+  }
+})().catch((e) => {
+  console.error("[bot] fatal:", e);
+  process.exit(1);
+});