perf(mornye): share chrome backdrops and scale blur to clarity

test/mornye_bottom_bar_test.dart

@@ -137,6 +137,44 @@ void main() {
 
   const albumBlue = Color(0xff464566);
 
+  testWidgets(
+    'player and navbar share a backdrop while moving capsules remain isolated',
+    (tester) async {
+      await pumpShell(tester, blur: true, liquidGlass: false);
+      void expectSharedBackdrop() {
+        final filters = find.descendant(
+          of: find.byType(MornyeBottomBar),
+          matching: find.byType(BackdropFilter),
+        );
+        final renderers = filters
+            .evaluate()
+            .map(
+              (element) => element.findRenderObject()! as RenderBackdropFilter,
+            )
+            .toList();
+        final shared = renderers
+            .where((filter) => filter.backdropKey != null)
+            .toList();
+        expect(shared, hasLength(2));
+        expect(shared[0].backdropKey, same(shared[1].backdropKey));
+        // Side capsules overlap the folding tabs and must not join their group.
+        expect(
+          renderers.where((filter) => filter.backdropKey == null),
+          hasLength(2),
+        );
+      }
+
+      expectSharedBackdrop();
+      chrome.value = true;
+      await tester.pump();
+      await tester.pump(const Duration(milliseconds: 190));
+      expectSharedBackdrop();
+      await tester.pumpAndSettle();
+      expectSharedBackdrop();
+      expect(tester.takeException(), isNull);
+    },
+  );
+
   for (final liquidGlass in [false, true]) {
     testWidgets(
       'navbar keeps its backdrop blurred throughout motion (liquid: $liquidGlass)',

test/mornye_glass_level_test.dart

@@ -1,3 +1,5 @@
+import 'dart:ui' as ui;
+
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -115,6 +117,54 @@ void main() {
     expect(tester.takeException(), isNull);
   });
 
+  testWidgets(
+    'low clarity uses a small blur and mid-range glass caps its radius',
+    (tester) async {
+      Future<ui.ImageFilter?> filterFor(double clarity, bool liquid) async {
+        await tester.pumpWidget(
+          ProviderScope(
+            key: UniqueKey(),
+            overrides: [
+              mornyeGlassLevelProvider.overrideWithValue(
+                liquid ? MornyeGlassLevel.liquid : MornyeGlassLevel.frosted,
+              ),
+            ],
+            child: MaterialApp(
+              theme: MornyeTheme.build(Brightness.light, glassClarity: clarity),
+              home: const MornyeGlass.navigation(
+                blurEnabled: true,
+                child: SizedBox(width: 200, height: 50),
+              ),
+            ),
+          ),
+        );
+        final filters = tester.widgetList<BackdropFilter>(
+          find.byType(BackdropFilter),
+        );
+        return filters.isEmpty ? null : filters.single.filter;
+      }
+
+      expect(await filterFor(0, false), isNull);
+      expect(await filterFor(0.1, false), isNull);
+      expect(
+        await filterFor(0.25, false),
+        ui.ImageFilter.blur(sigmaX: 4, sigmaY: 4),
+      );
+      expect(
+        await filterFor(0.1, true),
+        ui.ImageFilter.blur(sigmaX: 4, sigmaY: 4),
+      );
+      expect(
+        await filterFor(1, false),
+        ui.ImageFilter.blur(sigmaX: 8, sigmaY: 8),
+      );
+      expect(
+        await filterFor(1, true),
+        ui.ImageFilter.blur(sigmaX: 18, sigmaY: 18),
+      );
+    },
+  );
+
   for (final clarity in [0.0, 0.5]) {
     testWidgets('liquid tab and segment pills follow clarity ($clarity)', (
       tester,