fix: prefer fresh codex activity in conversation timestamps

src/lib/boss-projections.ts

@@ -355,6 +355,7 @@ function buildConversationItem(state: BossState, project: Project): Conversation
   const folderLabel = project.threadMeta?.folderName ?? "";
   const activityIconCount = deriveConversationActivityIconCount(state, project);
   const topPinnedLabel = isTopPinnedConversation(project) ? "置顶" : undefined;
+  const latestConversationActivityAt = deriveLatestConversationActivityAt(project);
   const groupMembers = project.isGroup
     ? project.groupMembers.map((member) => ({
         threadId: member.threadId,
@@ -379,8 +380,8 @@ function buildConversationItem(state: BossState, project: Project): Conversation
     activityIconCount,
     topPinnedLabel,
     manualPinned: Boolean(project.pinned && !project.systemPinned),
-    latestReplyAt: project.lastMessageAt,
-    latestReplyLabel: formatTimestampLabel(project.lastMessageAt),
+    latestReplyAt: latestConversationActivityAt,
+    latestReplyLabel: formatTimestampLabel(latestConversationActivityAt),
     unreadCount: project.unreadCount,
     riskLevel: project.riskLevel,
     activeDeviceCount: devices.length,
@@ -403,6 +404,31 @@ function buildConversationItem(state: BossState, project: Project): Conversation
   } satisfies ConversationItem;
 }
 
+function deriveLatestConversationActivityAt(project: Project) {
+  const candidates = [
+    project.lastMessageAt,
+    project.threadMeta?.lastObservedCodexActivityAt,
+    project.projectUnderstanding?.updatedAt,
+    project.updatedAt,
+  ].filter(Boolean) as string[];
+
+  let latest = candidates[0];
+  let latestTs = latest ? Date.parse(latest) : Number.NEGATIVE_INFINITY;
+
+  for (const candidate of candidates.slice(1)) {
+    const candidateTs = Date.parse(candidate);
+    if (!Number.isFinite(candidateTs)) {
+      continue;
+    }
+    if (!Number.isFinite(latestTs) || candidateTs > latestTs) {
+      latest = candidate;
+      latestTs = candidateTs;
+    }
+  }
+
+  return latest ?? project.lastMessageAt;
+}
+
 function deriveConversationActivityIconCount(state: BossState, project: Project): number {
   let count = 0;