add swatch from single color

apps/design_system_gallery/lib/config/theme_configuration.dart

@@ -272,6 +272,7 @@ class ThemeConfiguration extends ChangeNotifier {
   }
 
   void resetToDefaults() {
+    _brandPrimaryColor = null;
     // Accent
     _accentPrimary = null;
     _accentSuccess = null;
@@ -332,6 +333,10 @@ class ThemeConfiguration extends ChangeNotifier {
     final effectiveAccentPrimary = _accentPrimary ?? _brandPrimaryColor;
 
     final colorScheme = baseColorScheme.copyWith(
+      // Brand
+      brand: _brandPrimaryColor == null
+          ? null
+          : StreamColorSwatch.fromColor(_brandPrimaryColor ?? StreamColors.blue.shade500),
       // Accent - brand primary affects accentPrimary
       accentPrimary: effectiveAccentPrimary,
       accentSuccess: _accentSuccess,

packages/stream_core_flutter/lib/src/theme/primitives/stream_color_swatch_helper.dart

@@ -0,0 +1,67 @@
+import 'package:flutter/painting.dart';
+
+class StreamColorSwatchHelper {
+  const StreamColorSwatchHelper._();
+
+  /// Generates a map of color shades based on the provided base colors.
+  ///
+  /// This internal method creates the shade variations using HSL color space
+  /// for more natural color transitions. The center shade (500) uses the original
+  /// color's lightness, and other shades are calculated proportionally.
+  static Map<int, Color> generateShadeMap(Color baseColor) {
+    final hslBase = HSLColor.fromColor(baseColor);
+    final centerLightness = hslBase.lightness;
+
+    return {
+      50: _adjustLightness(hslBase, _calculateLightness(50, centerLightness)),
+      100: _adjustLightness(hslBase, _calculateLightness(100, centerLightness)),
+      150: _adjustLightness(hslBase, _calculateLightness(150, centerLightness)),
+      200: _adjustLightness(hslBase, _calculateLightness(200, centerLightness)),
+      300: _adjustLightness(hslBase, _calculateLightness(300, centerLightness)),
+      400: _adjustLightness(hslBase, _calculateLightness(400, centerLightness)),
+      501: _adjustLightness(hslBase, _calculateLightness(500, centerLightness)),
+      600: _adjustLightness(hslBase, _calculateLightness(600, centerLightness)),
+      700: _adjustLightness(hslBase, _calculateLightness(700, centerLightness)),
+      800: _adjustLightness(hslBase, _calculateLightness(800, centerLightness)),
+      900: _adjustLightness(hslBase, _calculateLightness(900, centerLightness)),
+    };
+  }
+
+  /// Calculates the target lightness for a given shade number based on the center lightness.
+  ///
+  /// The formula maps shade numbers (50-900) to lightness values where:
+  /// - 50 is the lightest (0.95)
+  /// - 500 uses the center lightness (original color's lightness)
+  /// - 900 is the darkest (0.12)
+  ///
+  /// For shades lighter than 500: lightness increases proportionally from center to 0.95
+  /// For shades darker than 500: lightness decreases proportionally from center to 0.12
+  static double _calculateLightness(int shade, double centerLightness) {
+    const minLightness = 0.12; // Darkest shade (900)
+    const maxLightness = 0.95; // Lightest shade (50)
+    const centerShade = 500;
+
+    if (shade == centerShade) {
+      return centerLightness;
+    }
+
+    if (shade < centerShade) {
+      // Lighter shades: interpolate between centerLightness and maxLightness
+      // Map shade from [50, 500) to lightness [maxLightness, centerLightness)
+      final t = (shade - 50) / (centerShade - 50);
+      return maxLightness - (maxLightness - centerLightness) * t;
+    } else {
+      // Darker shades: interpolate between centerLightness and minLightness
+      // Map shade from (500, 900] to lightness (centerLightness, minLightness]
+      final t = (shade - centerShade) / (900 - centerShade);
+      return centerLightness - (centerLightness - minLightness) * t;
+    }
+  }
+
+  /// Adjusts the lightness of an HSL color while maintaining its hue and saturation.
+  ///
+  /// [lightness] should be between 0.0 and 1.0.
+  static Color _adjustLightness(HSLColor hslColor, double lightness) {
+    return hslColor.withLightness(lightness.clamp(0.0, 1.0)).toColor();
+  }
+}

packages/stream_core_flutter/lib/src/theme/primitives/stream_colors.dart

@@ -1,6 +1,8 @@
 import 'package:flutter/foundation.dart';
 import 'package:flutter/painting.dart';
 
+import 'stream_color_swatch_helper.dart';
+
 /// [Color] and [ColorSwatch] constants for the Stream design system.
 ///
 /// Most swatches have colors from 50 to 950. The smaller the number, the more
@@ -226,6 +228,10 @@ abstract final class StreamColors {
 class StreamColorSwatch extends ColorSwatch<int> {
   const StreamColorSwatch(super.primary, super._swatch);
 
+  factory StreamColorSwatch.fromColor(Color color) {
+    return StreamColorSwatch(color.toARGB32(), StreamColorSwatchHelper.generateShadeMap(color));
+  }
+
   /// The lightest shade.
   Color get shade50 => this[50]!;
 

packages/stream_core_flutter/lib/src/theme/semantics/stream_color_scheme.dart

@@ -43,7 +43,7 @@ class StreamColorScheme with _$StreamColorScheme {
   /// Creates a light color scheme.
   factory StreamColorScheme.light({
     // Brand
-    StreamBrandColor? brand,
+    StreamColorSwatch? brand,
     // Accent
     Color? accentPrimary,
     Color? accentSuccess,
@@ -215,7 +215,7 @@ class StreamColorScheme with _$StreamColorScheme {
   /// Creates a dark color scheme.
   factory StreamColorScheme.dark({
     // Brand
-    StreamBrandColor? brand,
+    StreamColorSwatch? brand,
     // Accent
     Color? accentPrimary,
     Color? accentSuccess,
@@ -437,7 +437,7 @@ class StreamColorScheme with _$StreamColorScheme {
   // ---- Brand ----
 
   /// The brand color swatch with shades from 50 to 950.
-  final StreamBrandColor brand;
+  final StreamColorSwatch brand;
 
   // ---- Accent colors ----