fix(inspector): show encoding name in the combo selection box

The themed ComboBox's selection box renders via ToString() (DisplayMemberPath
only drives the dropdown items), so it showed the record's default
"TextEncodingOption { ... }". Override ToString() to return DisplayName.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: NeWbY100

ReScene.NET.Tests/TextEncodingOptionsTests.cs

@@ -31,4 +31,15 @@ public void AllEntries_HaveNonNullEncoding()
     {
         Assert.All(TextEncodingOptions.All, e => Assert.NotNull(e.Encoding));
     }
+
+    [Fact]
+    public void ToString_ReturnsDisplayName()
+    {
+        // The encoding ComboBox's selection box renders via ToString(), so it must be the
+        // friendly name — not the record's default "TextEncodingOption { ... }" form.
+        var utf8 = TextEncodingOptions.All[0];
+
+        Assert.Equal("UTF-8", utf8.ToString());
+        Assert.All(TextEncodingOptions.All, e => Assert.Equal(e.DisplayName, e.ToString()));
+    }
 }

ReScene.NET/Helpers/TextEncodingOption.cs

@@ -3,7 +3,12 @@
 namespace ReScene.NET.Helpers;
 
 /// <summary>A selectable text encoding: a human-friendly name plus the backing <see cref="Encoding"/>.</summary>
-public sealed record TextEncodingOption(string DisplayName, Encoding Encoding);
+public sealed record TextEncodingOption(string DisplayName, Encoding Encoding)
+{
+    // The themed ComboBox's selection box falls back to ToString() (DisplayMemberPath only drives
+    // the dropdown items), so present the friendly name rather than the record's default rendering.
+    public override string ToString() => DisplayName;
+}
 
 /// <summary>
 /// The curated set of encodings offered by the Inspector's Text view. CP437 and Windows-1252 are not