Fix RadioThemeData documentation issues (#89064)

packages/flutter/lib/src/material/radio_theme.dart

diff --git a/packages/flutter/lib/src/material/radio_theme.dart b/packages/flutter/lib/src/material/radio_theme.dart
index f0b7338..82e217f 100644
--- a/packages/flutter/lib/src/material/radio_theme.dart
+++ b/packages/flutter/lib/src/material/radio_theme.dart
@@ -30,6 +30,8 @@
 ///
 ///  * [ThemeData], which describes the overall theme information for the
 ///    application.
+///  * [RadioTheme], which is used by descendants to obtain the
+///    [RadioThemeData].
 @immutable
 class RadioThemeData with Diagnosticable {
   /// Creates a theme that can be used for [ThemeData.radioTheme].
@@ -44,33 +46,43 @@
 
   /// {@macro flutter.material.radio.mouseCursor}
   ///
-  /// If specified, overrides the default value of [Radio.mouseCursor].
+  /// If specified, overrides the default value of [Radio.mouseCursor]. The
+  /// default value is [MaterialStateMouseCursor.clickable].
   final MaterialStateProperty<MouseCursor?>? mouseCursor;
 
   /// {@macro flutter.material.radio.fillColor}
   ///
-  /// If specified, overrides the default value of [Radio.fillColor].
+  /// If specified, overrides the default value of [Radio.fillColor]. The
+  /// default value is the value of [ThemeData.disabledColor] in the disabled
+  /// state, [ThemeData.toggleableActiveColor] in the selected state, and
+  /// [ThemeData.unselectedWidgetColor] in the default state.
   final MaterialStateProperty<Color?>? fillColor;
 
   /// {@macro flutter.material.radio.overlayColor}
   ///
-  /// If specified, overrides the default value of [Radio.overlayColor].
+  /// If specified, overrides the default value of [Radio.overlayColor]. The
+  /// default value is [ThemeData.toggleableActiveColor] with alpha
+  /// [kRadialReactionAlpha], [ThemeData.focusColor] and [ThemeData.hoverColor]
+  /// in the pressed, focused, and hovered state.
   final MaterialStateProperty<Color?>? overlayColor;
 
   /// {@macro flutter.material.radio.splashRadius}
   ///
-  /// If specified, overrides the default value of [Radio.splashRadius].
+  /// If specified, overrides the default value of [Radio.splashRadius]. The
+  /// default value is [kRadialReactionRadius].
   final double? splashRadius;
 
   /// {@macro flutter.material.radio.materialTapTargetSize}
   ///
   /// If specified, overrides the default value of
-  /// [Radio.materialTapTargetSize].
+  /// [Radio.materialTapTargetSize]. The default value is the value of
+  /// [ThemeData.materialTapTargetSize].
   final MaterialTapTargetSize? materialTapTargetSize;
 
   /// {@macro flutter.material.radio.visualDensity}
   ///
-  /// If specified, overrides the default value of [Radio.visualDensity].
+  /// If specified, overrides the default value of [Radio.visualDensity]. The
+  /// default value is the value of [ThemeData.visualDensity].
   final VisualDensity? visualDensity;
 
   /// Creates a copy of this object but with the given fields replaced with the