tool_result preview 복원과 슬래시 명령 합성 일원화

목적:
- 긴 세션, 분기, 재시작 이후에도 tool_result preview 축약 상태를 더 안정적으로 유지합니다.
- 슬래시 팔레트와 실제 /토큰 실행 해석이 어긋나지 않도록 built-in command와 skill 우선순위를 같은 규칙으로 맞춥니다.

핵심 수정:
- AgentMessageInvariantHelper에 tool_use_id 기준 preview 맵/복원 helper를 추가했습니다.
- ChatSessionStateService는 분기 대화 생성 시 QueryPreviewContent를 함께 복사하고, 저장된 대화를 다시 열 때 누락된 preview를 복원합니다.
- ChatStorageService는 저장 직전에 누락된 tool_result preview를 먼저 채워 재시작 후 축약 상태가 흔들리지 않게 정리했습니다.
- SlashCommandCatalog에 exact token 충돌 해석용 ResolvePreferredCommand를 추가하고, ChatWindow.ParseSlashCommandAsync가 built-in/skill 후보를 함께 모아 같은 우선순위 규칙으로 실행 대상을 선택하도록 맞췄습니다.
- SlashCommandCatalogTests를 새로 추가하고 ChatSessionStateServiceTests를 확장해 preview 복원과 skill 우선 해석을 회귀 검증했습니다.
- README.md, docs/DEVELOPMENT.md를 2026-04-15 07:16 (KST) 기준으로 갱신했습니다.

검증:
- dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_preview_state\\ -p:IntermediateOutputPath=obj\\verify_preview_state\\
- dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "AgentToolResultBudgetTests|ChatSessionStateServiceTests" -p:OutputPath=bin\\verify_preview_state_tests\\ -p:IntermediateOutputPath=obj\\verify_preview_state_tests\\ (통과 38)
- dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify_command_resolution\\ -p:IntermediateOutputPath=obj\\verify_command_resolution\\
- dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter "SlashCommandCatalogTests|ChatSessionStateServiceTests|AgentToolResultBudgetTests|AgentCommandQueueTests" -p:OutputPath=bin\\verify_command_resolution_tests\\ -p:IntermediateOutputPath=obj\\verify_command_resolution_tests\\ (통과 50)

src/AxCopilot/Views/ChatWindow.xaml.cs

@@ -3607,7 +3607,44 @@ public partial class ChatWindow : Window
         {
             var firstSpace = trimmed.IndexOf(' ');
             var commandToken = (firstSpace >= 0 ? trimmed[..firstSpace] : trimmed).Trim();
-            if (SlashCommandCatalog.TryGetEntry(commandToken, out var entry))
+            var isDev = _activeTab is "Cowork" or "Code";
+            var exactEntries = new List<(string Cmd, string Label, bool IsSkill, int Priority)>();
+
+            if (SlashCommandCatalog.TryGetEntry(commandToken, out var entry)
+                && (entry.Tab == "all" || (isDev && entry.Tab == "dev")))
+            {
+                exactEntries.Add((
+                    Cmd: commandToken,
+                    Label: entry.Label,
+                    IsSkill: false,
+                    Priority: SlashCommandCatalog.GetBuiltInCommandPriority(commandToken)));
+            }
+
+            if (_settings.Settings.Llm.EnableSkillSystem)
+            {
+                EnsureSkillSystemLoadedForCurrentWorkspace();
+                exactEntries.AddRange(
+                    SkillService.MatchSlashCommand(commandToken)
+                        .Where(s => s.IsVisibleInTab(_activeTab))
+                        .Where(s => string.Equals("/" + s.Name, commandToken, StringComparison.OrdinalIgnoreCase))
+                        .Select(s => (
+                            Cmd: "/" + s.Name,
+                            Label: BuildSlashSkillLabel(s),
+                            IsSkill: true,
+                            Priority: SkillService.GetSkillSourcePriority(s.SourceScope))));
+            }
+
+            var preferredCommand = SlashCommandCatalog.ResolvePreferredCommand(commandToken, exactEntries);
+            if (preferredCommand.HasValue && preferredCommand.Value.IsSkill)
+            {
+                var compiled = await SkillService.BuildSlashInvocationAsync(input, GetCurrentWorkFolder(), ct);
+                if (compiled != null)
+                    return (compiled.SystemPrompt, compiled.DisplayText);
+            }
+
+            if (preferredCommand.HasValue
+                && !preferredCommand.Value.IsSkill
+                && SlashCommandCatalog.TryGetEntry(commandToken, out entry))
             {
                 // __HELP__는 특수 처리 (ParseSlashCommand에서는 무시)
                 if (entry.SystemPrompt == "__HELP__") return (null, input);

src/AxCopilot/Views/SlashCommandCatalog.cs

@@ -128,19 +128,42 @@ internal static class SlashCommandCatalog
         if (entries == null)
             return [];
 
+        return OrderEntries(entries)
+            .Select(entry => (entry.Cmd, entry.Label, entry.IsSkill, entry.Priority))
+            .Select(entry => (entry.Cmd, entry.Label, entry.IsSkill))
+            .ToList();
+    }
+
+    internal static (string Cmd, string Label, bool IsSkill)? ResolvePreferredCommand(
+        string commandToken,
+        IEnumerable<(string Cmd, string Label, bool IsSkill, int Priority)> entries)
+    {
+        if (string.IsNullOrWhiteSpace(commandToken) || entries == null)
+            return null;
+
+        var resolved = OrderEntries(entries.Where(entry =>
+                string.Equals(entry.Cmd, commandToken, StringComparison.OrdinalIgnoreCase)))
+            .FirstOrDefault();
+
+        return string.IsNullOrWhiteSpace(resolved.Cmd)
+            ? null
+            : (resolved.Cmd, resolved.Label, resolved.IsSkill);
+    }
+
+    private static IEnumerable<(string Cmd, string Label, bool IsSkill, int Priority)> OrderEntries(
+        IEnumerable<(string Cmd, string Label, bool IsSkill, int Priority)> entries)
+    {
         return entries
             .Where(entry => !string.IsNullOrWhiteSpace(entry.Cmd))
             .GroupBy(entry => entry.Cmd, StringComparer.OrdinalIgnoreCase)
             .Select(group => group
                 .OrderByDescending(entry => entry.Priority)
-                .ThenBy(entry => entry.IsSkill ? 1 : 0)
+                .ThenByDescending(entry => entry.IsSkill)
                 .ThenBy(entry => entry.Cmd, StringComparer.OrdinalIgnoreCase)
                 .First())
-            .Select(entry => (entry.Cmd, entry.Label, entry.IsSkill, entry.Priority))
             .OrderByDescending(entry => entry.Priority)
-            .ThenBy(entry => entry.Cmd, StringComparer.OrdinalIgnoreCase)
-            .Select(entry => (entry.Cmd, entry.Label, entry.IsSkill))
-            .ToList();
+            .ThenByDescending(entry => entry.IsSkill)
+            .ThenBy(entry => entry.Cmd, StringComparer.OrdinalIgnoreCase);
     }
 
     internal static bool TryGetEntry(string commandToken, out (string Label, string SystemPrompt, string Tab) entry)