refactor: centralize cursor key resolution with resolveCursorKey()

Replace all manual cursor key construction (hardcoded chatJid:reviewer,
chatJid:arbiter, pairedCursorKey, 3-way ternary) with a single
resolveCursorKey(chatJid, taskStatus) function.

- Removed pairedCursorKey import (no longer needed)
- Removed loopIsReviewerTurn, loopIsArbiterTurn intermediate variables
- All cursor key logic now flows through one function that maps
  task status to the correct role-specific key

src/message-runtime-rules.ts

@@ -39,6 +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.
+ */
+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;
+  }
+}
+
 export function createImplicitContinuationTracker(idleTimeout: number) {
   const implicitContinuationUntil = new Map<string, number>();
 

src/message-runtime.ts

@@ -41,7 +41,7 @@ import { isTriggerAllowed, loadSenderAllowlist } from './sender-allowlist.js';
 import {
   advanceLastAgentCursor,
   createImplicitContinuationTracker,
-  pairedCursorKey,
+  resolveCursorKey,
   filterLoopingPairedBotMessages,
   getProcessableMessages,
   hasAllowedTrigger,
@@ -634,7 +634,7 @@ export function createMessageRuntime(deps: MessageRuntimeDeps): {
               deps.saveState,
               chatJid,
               cursor,
-              `${chatJid}:reviewer`,
+              resolveCursorKey(chatJid, pendingReviewTask?.status),
             );
           }
 
@@ -665,7 +665,7 @@ export function createMessageRuntime(deps: MessageRuntimeDeps): {
               deps.saveState,
               chatJid,
               cursor,
-              `${chatJid}:arbiter`,
+              resolveCursorKey(chatJid, pendingReviewTask?.status),
             );
           }
 
@@ -839,9 +839,7 @@ export function createMessageRuntime(deps: MessageRuntimeDeps): {
         : useReviewerChannel
           ? reviewerChannel
           : channel;
-      const cursorKey = useArbiterChannel
-        ? `${chatJid}:arbiter`
-        : pairedCursorKey(chatJid, !!useReviewerChannel);
+      const cursorKey = resolveCursorKey(chatJid, pendingTaskForChannel?.status);
 
       // Arbiter turns use a dedicated context prompt; regular turns use formatted messages.
       let prompt: string;
@@ -1049,17 +1047,7 @@ export function createMessageRuntime(deps: MessageRuntimeDeps): {
             const loopPendingTask = isPairedRoomJid(chatJid)
               ? getLatestOpenPairedTaskForChat(chatJid)
               : null;
-            const loopIsReviewerTurn =
-              !!loopPendingTask &&
-              (loopPendingTask.status === 'review_ready' ||
-                loopPendingTask.status === 'in_review');
-            const loopIsArbiterTurn =
-              !!loopPendingTask &&
-              (loopPendingTask.status === 'arbiter_requested' ||
-                loopPendingTask.status === 'in_arbitration');
-            const loopCursorKey = loopIsArbiterTurn
-              ? `${chatJid}:arbiter`
-              : pairedCursorKey(chatJid, loopIsReviewerTurn);
+            const loopCursorKey = resolveCursorKey(chatJid, loopPendingTask?.status);
 
             const rawPendingMessages = getMessagesSinceSeq(
               chatJid,