fix(conversations): 修复会话标识与解决后跳转

frontend/app/javascript/dashboard/helper/conversationNavigation.js

@@ -0,0 +1,10 @@
+export const getAdjacentConversationId = (conversationIds, currentId) => {
+  const currentIndex = conversationIds.indexOf(currentId);
+  if (currentIndex === -1) return null;
+
+  return (
+    conversationIds[currentIndex + 1] ??
+    conversationIds[currentIndex - 1] ??
+    null
+  );
+};

frontend/app/javascript/dashboard/helper/specs/conversationNavigation.spec.js

@@ -0,0 +1,21 @@
+import { getAdjacentConversationId } from '../conversationNavigation';
+
+describe('getAdjacentConversationId', () => {
+  const conversationIds = [15, 19, 25];
+
+  it('selects the immediate next conversation', () => {
+    expect(getAdjacentConversationId(conversationIds, 15)).toBe(19);
+  });
+
+  it('selects the previous conversation for the last item', () => {
+    expect(getAdjacentConversationId(conversationIds, 25)).toBe(19);
+  });
+
+  it('returns null for a single-item list', () => {
+    expect(getAdjacentConversationId([15], 15)).toBeNull();
+  });
+
+  it('returns null when the current conversation is absent', () => {
+    expect(getAdjacentConversationId(conversationIds, 99)).toBeNull();
+  });
+});