탭 전환 빈 대화 누적 방지: 저장 게이트 + 목록 노이즈 필터

- ChatSessionStateService.SaveCurrentConversation에 persistable-content 검사 추가

- 무의미한 빈 새 대화는 저장/탭 기억 대상에서 제외

- ChatWindow 대화 목록에서 빈 노이즈 항목 필터링

- ChatSessionStateServiceTests 회귀 추가 및 문서 이력(2026-04-04 15:48 KST) 동기화

src/AxCopilot/Services/ChatSessionStateService.cs

@@ -91,6 +91,7 @@ public sealed class ChatSessionStateService
     {
         var normalizedTab = NormalizeTab(tab);
         var rememberedId = GetConversationId(normalizedTab);
+        var hadRememberedConversation = !string.IsNullOrWhiteSpace(rememberedId);
         if (!string.IsNullOrWhiteSpace(rememberedId))
         {
             var loaded = storage.Load(rememberedId);
@@ -115,6 +116,30 @@ public sealed class ChatSessionStateService
                 RememberConversation(normalizedTab, null);
         }
 
+        if (!hadRememberedConversation)
+        {
+            var latestMeta = storage.LoadAllMeta()
+                .Where(c => string.Equals(NormalizeTab(c.Tab), normalizedTab, StringComparison.OrdinalIgnoreCase))
+                .OrderByDescending(c => c.Pinned)
+                .ThenByDescending(c => c.UpdatedAt)
+                .FirstOrDefault();
+            if (latestMeta != null)
+            {
+                var loaded = storage.Load(latestMeta.Id);
+                if (loaded != null)
+                {
+                    loaded.Tab = normalizedTab;
+                    var normalized = NormalizeLoadedConversation(loaded);
+                    CurrentConversation = loaded;
+                    RememberConversation(normalizedTab, loaded.Id);
+                    if (normalized)
+                        try { storage.Save(loaded); } catch { }
+                    return loaded;
+                }
+            }
+        }
+
+        RememberConversation(normalizedTab, null);
         return CreateFreshConversation(normalizedTab, settings);
     }
 
@@ -209,13 +234,15 @@ public sealed class ChatSessionStateService
         var conv = CurrentConversation;
         if (conv == null) return;
 
-        try { storage.Save(conv); } catch { }
         var conversationTab = NormalizeTab(conv.Tab);
-        if (conv.Messages.Count > 0
-            || (conv.ExecutionEvents?.Count ?? 0) > 0
-            || (conv.AgentRunHistory?.Count ?? 0) > 0
-            || (conv.DraftQueueItems?.Count ?? 0) > 0)
-            RememberConversation(conversationTab, conv.Id);
+        if (!HasPersistableContent(conv))
+        {
+            RememberConversation(conversationTab, null);
+            return;
+        }
+
+        try { storage.Save(conv); } catch { }
+        RememberConversation(conversationTab, conv.Id);
     }
 
     public void ClearCurrentConversation(string tab)
@@ -571,6 +598,26 @@ public sealed class ChatSessionStateService
         return "Chat";
     }
 
+    private static bool HasPersistableContent(ChatConversation conv)
+    {
+        if ((conv.Messages?.Count ?? 0) > 0) return true;
+        if ((conv.ExecutionEvents?.Count ?? 0) > 0) return true;
+        if ((conv.AgentRunHistory?.Count ?? 0) > 0) return true;
+        if ((conv.DraftQueueItems?.Count ?? 0) > 0) return true;
+        if (conv.Pinned) return true;
+        if (!string.IsNullOrWhiteSpace(conv.WorkFolder)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.SystemCommand)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.ParentId)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.Permission)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.DataUsage)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.OutputFormat)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.Mood)) return true;
+        if (!string.IsNullOrWhiteSpace(conv.Preview)) return true;
+        if (!string.Equals(conv.Category, ChatCategory.General, StringComparison.OrdinalIgnoreCase)) return true;
+        if (!string.Equals((conv.Title ?? "").Trim(), "새 대화", StringComparison.OrdinalIgnoreCase)) return true;
+        return false;
+    }
+
     private static bool NormalizeLoadedConversation(ChatConversation conversation)
     {
         var changed = false;