Add Phase 4 TUI enhancements and refactor ResourceEditorWindow

Features added:
- Undo/Redo system with operation history (Ctrl+Z/Ctrl+Y)
- Code scanning integration (F7) with usage filters
- Context menus on right-click
- Clipboard support (Ctrl+C/Ctrl+V)
- Enhanced search with clear button, match counter, F3/Shift+F3
- Progress bars for translation and scanning operations
- Visual status indicators with color-coded icons
- StatusBar upgrade with code scan statistics

Refactoring:
- Split ResourceEditorWindow.cs (4,225 lines) into 7 partial classes (4,471 lines)
- Organized by concern: Main, Layout, Data, Events, Dialogs, Operations, Filters
- Improves maintainability and makes future enhancements easier

Testing:
- Added OperationHistoryTests.cs with 15 comprehensive unit tests
- All 488 tests passing

Author: nickprotop

Commands/EditCommand.cs

@@ -19,6 +19,7 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
+using System.ComponentModel;
 using LocalizationManager.Core;
 using LocalizationManager.Core.Models;
 using LocalizationManager.UI;
@@ -31,16 +32,37 @@ namespace LocalizationManager.Commands;
 /// <summary>
 /// Command to launch the interactive TUI editor.
 /// </summary>
-public class EditCommand : Command<BaseCommandSettings>
+public class EditCommand : Command<EditCommand.Settings>
 {
-    public override int Execute(CommandContext context, BaseCommandSettings settings, CancellationToken cancellationToken = default)
+    public class Settings : BaseCommandSettings
+    {
+        [CommandOption("--source-path <PATH>")]
+        [Description("Path to source code directory for code scanning. Defaults to parent directory of resource path.")]
+        public string? SourcePath { get; set; }
+    }
+
+    public override int Execute(CommandContext context, Settings settings, CancellationToken cancellationToken = default)
     {
         // Load configuration if available
         settings.LoadConfiguration();
 
         var resourcePath = settings.GetResourcePath();
         var defaultCode = settings.LoadedConfiguration?.DefaultLanguageCode ?? "default";
 
+        // Determine source path for code scanning (same logic as ScanCommand)
+        // Convert to absolute path first to handle relative paths correctly
+        var absoluteResourcePath = Path.GetFullPath(resourcePath).TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        string sourcePath;
+        if (settings.SourcePath != null)
+        {
+            sourcePath = Path.GetFullPath(settings.SourcePath).TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        }
+        else
+        {
+            var parent = Directory.GetParent(absoluteResourcePath);
+            sourcePath = parent?.FullName ?? absoluteResourcePath;
+        }
+
         try
         {
             // Discover languages
@@ -73,7 +95,7 @@ public override int Execute(CommandContext context, BaseCommandSettings settings
 
             // Launch TUI
             Application.Init();
-            Application.Run(new ResourceEditorWindow(resourceFiles, parser, defaultCode, settings.LoadedConfiguration));
+            Application.Run(new ResourceEditorWindow(resourceFiles, parser, defaultCode, sourcePath, settings.LoadedConfiguration));
             Application.Shutdown();
 
             return 0;

Commands/ScanCommand.cs

@@ -62,8 +62,19 @@ public override int Execute(CommandContext context, Settings settings, Cancellat
         var format = settings.GetOutputFormat();
         var isTableFormat = format == OutputFormat.Table;
 
-        // Determine source path
-        var sourcePath = settings.SourcePath ?? Directory.GetParent(resourcePath)?.FullName ?? resourcePath;
+        // Determine source path - convert to absolute path first to handle relative paths correctly
+        // Trim trailing slashes to ensure Directory.GetParent works correctly
+        var absoluteResourcePath = Path.GetFullPath(resourcePath).TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        string sourcePath;
+        if (settings.SourcePath != null)
+        {
+            sourcePath = Path.GetFullPath(settings.SourcePath).TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        }
+        else
+        {
+            var parent = Directory.GetParent(absoluteResourcePath);
+            sourcePath = parent?.FullName ?? absoluteResourcePath;
+        }
 
         if (!Directory.Exists(sourcePath))
         {

Commands/ValidateCommand.cs

@@ -660,12 +660,19 @@ private void ScanCodeForDuplicates(
         if (!allDuplicateKeys.Any())
             return;
 
-        // Determine source path
-        var sourcePath = settings.SourcePath;
-        if (string.IsNullOrEmpty(sourcePath))
+        // Determine source path - convert to absolute path first to handle relative paths correctly
+        // Trim trailing slashes to ensure Directory.GetParent works correctly
+        var absoluteResourcePath = Path.GetFullPath(resourcePath).TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        string sourcePath;
+        if (!string.IsNullOrEmpty(settings.SourcePath))
+        {
+            sourcePath = Path.GetFullPath(settings.SourcePath).TrimEnd(Path.DirectorySeparatorChar, Path.AltDirectorySeparatorChar);
+        }
+        else
         {
             // Default to parent directory of resource path
-            sourcePath = Directory.GetParent(resourcePath)?.FullName ?? resourcePath;
+            var parent = Directory.GetParent(absoluteResourcePath);
+            sourcePath = parent?.FullName ?? absoluteResourcePath;
         }
 
         if (!Directory.Exists(sourcePath))