refactor(ui): merge the one-expression converters into SimpleConverters.cs

Six files of three lines each. NotNullToBool is gone entirely — Avalonia
ships ObjectConverters.IsNotNull, so TaskRowView binds that directly.

src/ClaudeDo.Ui/Converters/BoolToDraftOpacityConverter.cs

@@ -1,13 +0,0 @@
-using System;
-using System.Globalization;
-using Avalonia.Data.Converters;
-
-namespace ClaudeDo.Ui.Converters;
-
-public sealed class BoolToDraftOpacityConverter : IValueConverter
-{
-    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => value is true ? 0.7 : 1.0;
-    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => throw new NotSupportedException();
-}

src/ClaudeDo.Ui/Converters/BoolToItalicConverter.cs

@@ -1,14 +0,0 @@
-using System;
-using System.Globalization;
-using Avalonia.Data.Converters;
-using Avalonia.Media;
-
-namespace ClaudeDo.Ui.Converters;
-
-public sealed class BoolToItalicConverter : IValueConverter
-{
-    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => value is true ? FontStyle.Italic : FontStyle.Normal;
-    public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => throw new NotSupportedException();
-}

src/ClaudeDo.Ui/Converters/NotHeaderRowConverter.cs

@@ -1,18 +0,0 @@
-using System.Globalization;
-using Avalonia.Data.Converters;
-using ClaudeDo.Ui.ViewModels.Islands;
-
-namespace ClaudeDo.Ui.Converters;
-
-// Drives ListBoxItem.Focusable for TasksIslandView's flat Rows list: a HeaderRow container must
-// not be a tab stop, a TaskRowViewModel container must behave like any other row.
-public class NotHeaderRowConverter : IValueConverter
-{
-    public static NotHeaderRowConverter Instance { get; } = new();
-
-    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => value is not HeaderRow;
-
-    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => throw new NotSupportedException();
-}

src/ClaudeDo.Ui/Converters/NotNullToBoolConverter.cs

@@ -1,15 +0,0 @@
-using System.Globalization;
-using Avalonia.Data.Converters;
-
-namespace ClaudeDo.Ui.Converters;
-
-public class NotNullToBoolConverter : IValueConverter
-{
-    public static NotNullToBoolConverter Instance { get; } = new();
-
-    public object Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => value is not null;
-
-    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => throw new NotSupportedException();
-}

src/ClaudeDo.Ui/Converters/SimpleConverters.cs

@@ -0,0 +1,53 @@
+using System.Globalization;
+using Avalonia.Data.Converters;
+using Avalonia.Media;
+using ClaudeDo.Ui.ViewModels.Islands;
+
+namespace ClaudeDo.Ui.Converters;
+
+// One-expression converters. Each is only worth a class because Avalonia XAML can't
+// instantiate a generic FuncValueConverter as a resource; they stay one per type so the
+// x:Key names in App.axaml keep resolving. Anything with real logic gets its own file.
+
+public sealed class UpperCaseConverter : OneWayConverter
+{
+    public static UpperCaseConverter Instance { get; } = new();
+    public override object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value?.ToString()?.ToUpperInvariant();
+}
+
+public sealed class StrikeIfTrueConverter : OneWayConverter
+{
+    public static StrikeIfTrueConverter Instance { get; } = new();
+    public override object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value is true ? TextDecorations.Strikethrough : null;
+}
+
+public sealed class BoolToItalicConverter : OneWayConverter
+{
+    public override object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value is true ? FontStyle.Italic : FontStyle.Normal;
+}
+
+public sealed class BoolToDraftOpacityConverter : OneWayConverter
+{
+    public override object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value is true ? 0.7 : 1.0;
+}
+
+// Drives ListBoxItem.Focusable for TasksIslandView's flat Rows list: a HeaderRow container must
+// not be a tab stop, a TaskRowViewModel container must behave like any other row.
+public sealed class NotHeaderRowConverter : OneWayConverter
+{
+    public static NotHeaderRowConverter Instance { get; } = new();
+    public override object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => value is not HeaderRow;
+}
+
+public abstract class OneWayConverter : IValueConverter
+{
+    public abstract object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture);
+
+    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        => throw new NotSupportedException();
+}

src/ClaudeDo.Ui/Converters/StrikeIfTrueConverter.cs

@@ -1,16 +0,0 @@
-using System.Globalization;
-using Avalonia.Data.Converters;
-using Avalonia.Media;
-
-namespace ClaudeDo.Ui.Converters;
-
-public class StrikeIfTrueConverter : IValueConverter
-{
-    public static StrikeIfTrueConverter Instance { get; } = new();
-
-    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => value is true ? TextDecorations.Strikethrough : null;
-
-    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => throw new NotSupportedException();
-}

src/ClaudeDo.Ui/Converters/UpperCaseConverter.cs

@@ -1,15 +0,0 @@
-using System.Globalization;
-using Avalonia.Data.Converters;
-
-namespace ClaudeDo.Ui.Converters;
-
-public class UpperCaseConverter : IValueConverter
-{
-    public static UpperCaseConverter Instance { get; } = new();
-
-    public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => value?.ToString()?.ToUpperInvariant();
-
-    public object ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
-        => throw new NotSupportedException();
-}