refactor: extract resolveActiveRole() as single source of status→role mapping

resolveCursorKey and resolveChannel both duplicated the same
taskStatus→role switch. Now resolveActiveRole() is the single
mapping, and both functions derive from it.

src/message-runtime-rules.ts

@@ -39,28 +39,30 @@ export function pairedCursorKey(
   return isReviewerTurn ? `${chatJid}:reviewer` : chatJid;
 }
 
-/**
- * Auto-resolve the cursor key based on current paired task status.
- * Non-paired rooms always return chatJid.
- * Paired rooms return role-specific keys so owner/reviewer/arbiter
- * cursors are independent.
- */
+/** Map task status to the active role. */
+export function resolveActiveRole(
+  taskStatus?: string | null,
+): 'owner' | 'reviewer' | 'arbiter' {
+  switch (taskStatus) {
+    case 'review_ready':
+    case 'in_review':
+      return 'reviewer';
+    case 'arbiter_requested':
+    case 'in_arbitration':
+      return 'arbiter';
+    default:
+      return 'owner';
+  }
+}
+
+/** Cursor key for a role. Owner uses chatJid, others use chatJid:role. */
 export function resolveCursorKey(
   chatJid: string,
   taskStatus?: string | null,
 ): string {
   if (!isPairedRoomJid(chatJid)) return chatJid;
-  if (!taskStatus) return chatJid;
-  switch (taskStatus) {
-    case 'review_ready':
-    case 'in_review':
-      return `${chatJid}:reviewer`;
-    case 'arbiter_requested':
-    case 'in_arbitration':
-      return `${chatJid}:arbiter`;
-    default:
-      return chatJid;
-  }
+  const role = resolveActiveRole(taskStatus);
+  return role === 'owner' ? chatJid : `${chatJid}:${role}`;
 }
 
 export function createImplicitContinuationTracker(idleTimeout: number) {