Fix voice join against LiveKit 0.13+ and tidy up command messages

revoice.js reads `room.isConnected()`, but @livekit/rtc-node turned that
into a getter, so every join threw "this.room.isConnected is not a
function" before the bot ever reached the channel. The player no longer
touches that getter: readiness comes from the connection's own join /
roomfetched events and is cleared when it reports the offline state.

Also delete the invoking chat message once a command is recognised
(DELETE_COMMAND_MESSAGES, on by default) so channels stay readable;
failures are non-fatal since it needs ManageMessages.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/config.ts

@@ -27,6 +27,11 @@ const schema = z.object({
   STOAT_API_URL: z.string().url(),
   STOAT_BOT_TOKEN: z.string().min(1),
   COMMAND_PREFIX: z.string().min(1).default("!"),
+  /** Remove the invoking message after a command is recognised. Needs ManageMessages. */
+  DELETE_COMMAND_MESSAGES: z
+    .enum(["true", "false"])
+    .default("true")
+    .transform((value) => value === "true"),
 
   PORT: z.coerce.number().int().positive().default(3005),
   HOST: z.string().default("0.0.0.0"),