feat: make notifyBotToken/adminUserId optional

The client never sends pairing notifications (the server does); these
Discord fields were required but unused. Make them optional + drop from
the config schema's required list. Back-compat: still accepted if set.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugin/core/config.ts

@@ -1,8 +1,12 @@
 export interface YonexusClientConfig {
   mainHost: string;
   identifier: string;
-  notifyBotToken: string;
-  adminUserId: string;
+  /**
+   * Optional. The client never sends pairing notifications (the server
+   * does); accepted for back-compat but no longer required.
+   */
+  notifyBotToken?: string;
+  adminUserId?: string;
 }
 
 export class YonexusClientConfigError extends Error {
@@ -44,15 +48,9 @@ export function validateYonexusClientConfig(raw: unknown): YonexusClientConfig {
     issues.push("identifier is required");
   }
 
+  // Optional (back-compat): the client does not send notifications.
   const rawNotifyBotToken = source.notifyBotToken;
-  if (!isNonEmptyString(rawNotifyBotToken)) {
-    issues.push("notifyBotToken is required");
-  }
-
   const rawAdminUserId = source.adminUserId;
-  if (!isNonEmptyString(rawAdminUserId)) {
-    issues.push("adminUserId is required");
-  }
 
   if (issues.length > 0) {
     throw new YonexusClientConfigError(issues);
@@ -60,13 +58,15 @@ export function validateYonexusClientConfig(raw: unknown): YonexusClientConfig {
 
   const mainHost = (rawMainHost as string).trim();
   const identifier = (rawIdentifier as string).trim();
-  const notifyBotToken = (rawNotifyBotToken as string).trim();
-  const adminUserId = (rawAdminUserId as string).trim();
 
   return {
     mainHost,
     identifier,
-    notifyBotToken,
-    adminUserId
+    notifyBotToken: isNonEmptyString(rawNotifyBotToken)
+      ? rawNotifyBotToken.trim()
+      : undefined,
+    adminUserId: isNonEmptyString(rawAdminUserId)
+      ? rawAdminUserId.trim()
+      : undefined
   };
 }