Add project restore files and NuGet cache for GsaViewer

- Created project.nuget.cache to store NuGet package cache information.
- Added project.packagespec.json to define project restore settings and dependencies.
- Included rider.project.restore.info for Rider IDE integration.

GsaEditor/ViewModels/EntryViewModel.cs

@@ -0,0 +1,93 @@
+using CommunityToolkit.Mvvm.ComponentModel;
+using GsaEditor.Core.Models;
+
+namespace GsaEditor.ViewModels;
+
+/// <summary>
+/// Wraps a <see cref="GsaEntry"/> for display in the details panel.
+/// </summary>
+public partial class EntryViewModel : ViewModelBase
+{
+    private readonly GsaEntry _entry;
+
+    [ObservableProperty]
+    private string _alias = string.Empty;
+
+    [ObservableProperty]
+    private bool _isCompressed;
+
+    /// <summary>
+    /// Callback invoked when entry data is modified (compression toggle, alias change).
+    /// </summary>
+    public Action? OnModified { get; set; }
+
+    public EntryViewModel(GsaEntry entry)
+    {
+        _entry = entry;
+        _alias = entry.Alias;
+        _isCompressed = entry.IsCompressed;
+    }
+
+    /// <summary>
+    /// The underlying <see cref="GsaEntry"/>.
+    /// </summary>
+    public GsaEntry Entry => _entry;
+
+    /// <summary>
+    /// Original (decompressed) file size in bytes.
+    /// </summary>
+    public uint OriginalSize => _entry.OriginalLength;
+
+    /// <summary>
+    /// Compressed file size in bytes.
+    /// </summary>
+    public uint CompressedSize => _entry.CompressedLength;
+
+    /// <summary>
+    /// Compression ratio as a percentage (0–100). Higher means more compression.
+    /// </summary>
+    public string CompressionRatio => OriginalSize > 0
+        ? $"{(1.0 - (double)CompressedSize / OriginalSize) * 100.0:F1}%"
+        : "0.0%";
+
+    /// <summary>
+    /// Human-readable original size string.
+    /// </summary>
+    public string OriginalSizeText => FormatSize(OriginalSize);
+
+    /// <summary>
+    /// Human-readable compressed size string.
+    /// </summary>
+    public string CompressedSizeText => FormatSize(CompressedSize);
+
+    partial void OnAliasChanged(string value)
+    {
+        if (_entry.Alias != value)
+        {
+            _entry.Alias = value;
+            OnModified?.Invoke();
+        }
+    }
+
+    partial void OnIsCompressedChanged(bool value)
+    {
+        if (_entry.IsCompressed != value)
+        {
+            var decompressed = _entry.GetDecompressedData();
+            _entry.SetData(decompressed, value);
+            OnPropertyChanged(nameof(OriginalSize));
+            OnPropertyChanged(nameof(CompressedSize));
+            OnPropertyChanged(nameof(CompressionRatio));
+            OnPropertyChanged(nameof(OriginalSizeText));
+            OnPropertyChanged(nameof(CompressedSizeText));
+            OnModified?.Invoke();
+        }
+    }
+
+    private static string FormatSize(long bytes)
+    {
+        if (bytes < 1024) return $"{bytes} B";
+        if (bytes < 1024 * 1024) return $"{bytes / 1024.0:F1} KB";
+        return $"{bytes / (1024.0 * 1024.0):F1} MB";
+    }
+}