refine: add milky translucency and curved reflections to Dock

mobile/test/widgets/glass_material_test.dart

@@ -9,6 +9,25 @@ import 'package:hepan_everyday/widgets/glass_dock.dart';
 import 'package:hepan_everyday/widgets/glass_refraction.dart';
 
 void main() {
+  testWidgets(
+    'Dock has a milky white body while transmitting a dark backdrop',
+    (tester) async {
+      final pixels = await _render(
+        tester,
+        GlassDock(selectedIndex: 0, onSelected: (_) {}),
+        backdropColor: const Color(0xFF162536),
+        preview: true,
+        previewName: 'liquid-glass-milky-dark.png',
+      );
+      // Away from icons and the bevel: white glass lifts the dark background,
+      // while its original cool colour remains visible through the material.
+      final red = _channel(pixels, 160, 43, 0);
+      final green = _channel(pixels, 160, 43, 1);
+      expect(red, greaterThan(45));
+      expect(red, lessThan(90));
+      expect(green - red, closeTo(13, 6));
+    },
+  );
   testWidgets('resting cursor is neutral grey and clears while held', (
     tester,
   ) async {
@@ -21,6 +40,8 @@ void main() {
     // Sample beside the visible label, away from icon glow and glass rims.
     final selected = _channel(resting, 16, 43, 0);
     final base = _channel(resting, 160, 43, 0);
+    // On a white page the white glass must not turn into a grey veil.
+    expect(base, greaterThanOrEqualTo(240));
     expect(base - selected, greaterThan(20));
     expect((_channel(resting, 16, 43, 2) - selected).abs(), lessThan(12));
     final held = await _render(
@@ -64,11 +85,11 @@ void main() {
       final red = _channel(pixels, 16, 40, 0);
       final green = _channel(pixels, 16, 40, 1);
       final blue = _channel(pixels, 16, 40, 2);
-      expect(red, lessThan(85));
-      expect(green - red, greaterThan(95));
-      // The strongest resting tint (34%) and base veil (5%) retain about 63%
-      // of the source's 210-level blue/red contrast, including the shorter rim.
-      expect(blue - red, greaterThan(130));
+      expect(red, lessThan(115));
+      expect(green - red, greaterThanOrEqualTo(80));
+      // The milky base and resting grey lens still transmit over half of the
+      // cyan source's 210-level blue/red contrast rather than becoming opaque.
+      expect(blue - red, greaterThan(105));
     },
   );
 
@@ -166,6 +187,7 @@ Future<ByteData> _render(
   double stripeWidth = 2,
   bool gradient = false,
   bool preview = false,
+  String? previewName,
   Offset offset = Offset.zero,
   Color backdropColor = const Color(0xFF14B4E6),
   bool held = false,
@@ -246,11 +268,13 @@ Future<ByteData> _render(
       final png = (await previewImage.toByteData(
         format: ui.ImageByteFormat.png,
       ))!;
-      final name = backdropColor == Colors.white
-          ? held
-                ? 'liquid-glass-held.png'
-                : 'liquid-glass-rest.png'
-          : 'liquid-glass-detail.png';
+      final name =
+          previewName ??
+          (backdropColor == Colors.white
+              ? held
+                    ? 'liquid-glass-held.png'
+                    : 'liquid-glass-rest.png'
+              : 'liquid-glass-detail.png');
       final output = File('../dist/screenshots/$name');
       await output.parent.create(recursive: true);
       await output.writeAsBytes(png.buffer.asUint8List());