fix: 删除bot后重置activeBotId，编辑立即更新名称，config fetch await防空值

1. 删除活跃bot后将activeBotId置null，由fetchBots自动选新的
2. updateBot同时更新内存中的name（无需重启即可看到名称变化）
3. openEditBot改为async await config请求，失败时用bot名称做fallback

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/bot/manager.ts

@@ -107,7 +107,12 @@ export class BotManager {
       defaultChannel: params.defaultChannel ?? existing.defaultChannel,
       channelPassword: params.channelPassword ?? existing.channelPassword,
     });
-    this.logger.info({ botId: id }, "Bot instance config updated (restart to apply)");
+    // Update in-memory name immediately (other fields need reconnect)
+    const bot = this.bots.get(id);
+    if (bot && params.name) {
+      bot.name = params.name;
+    }
+    this.logger.info({ botId: id }, "Bot instance config updated (connection changes need restart)");
   }
 
   getBotConfig(id: string): import("../data/database.js").BotInstance | undefined {