tidy the theme switcher popover (T-237)

Per demo feedback on the T-234 status-bar popover: collapse the -hc
theme rows into a single 'High contrast' toggle at the top (applies the
chosen base theme's -hc sibling live, falling back to the base when none
exists); list base themes only, sorted by display name; widen 240->280
and ellipsize rows so 'Catppuccin Mocha' no longer wraps; swap the swatch
dot for the Phosphor palette icon; lowercase the bar label to match the
all-lowercase status bar (proper case kept in the a11y label).

New pure theme_families helpers (base/sibling/resolve), unit-tested.
Modal picker_view consistency + the status-bar right-alignment remain on
T-237.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/builtin/theme_picker/theme_families_test.dart

@@ -0,0 +1,43 @@
+/// Tests for the theme-family helpers (T-237).
+library;
+
+import 'package:clide/builtin/theme_picker/src/theme_families.dart';
+import 'package:clide/kernel/kernel.dart';
+import 'package:test/test.dart';
+
+ThemeDefinition _def(String name, String display) => ThemeDefinition(name: name, displayName: display, dark: true, palette: Palette(const {}));
+
+void main() {
+  final all = [
+    _def('clide', 'Clide'),
+    _def('clide-hc', 'Clide (high contrast)'),
+    _def('midnight', 'Midnight'),
+    _def('midnight-hc', 'Midnight (high contrast)'),
+    _def('catppuccin-mocha', 'Catppuccin Mocha'),
+    _def('catppuccin-mocha-hc', 'Catppuccin Mocha (high contrast)'),
+    _def('paper', 'Paper'), // no -hc sibling in this fixture
+  ];
+
+  test('isHcName / baseThemeName', () {
+    expect(isHcName('midnight-hc'), isTrue);
+    expect(isHcName('midnight'), isFalse);
+    expect(baseThemeName('midnight-hc'), 'midnight');
+    expect(baseThemeName('catppuccin-mocha-hc'), 'catppuccin-mocha');
+    expect(baseThemeName('clide'), 'clide');
+  });
+
+  test('baseThemes drops -hc/-cb and sorts by display name', () {
+    final bases = baseThemes(all).map((t) => t.name).toList();
+    expect(bases, ['catppuccin-mocha', 'clide', 'midnight', 'paper']); // alphabetical by display
+    expect(bases.any(isHcName), isFalse);
+  });
+
+  test('hasHcSibling + resolveThemeName', () {
+    expect(hasHcSibling(all, 'midnight'), isTrue);
+    expect(hasHcSibling(all, 'paper'), isFalse);
+    expect(resolveThemeName(all, 'midnight', highContrast: true), 'midnight-hc');
+    expect(resolveThemeName(all, 'midnight', highContrast: false), 'midnight');
+    // No sibling → falls back to the base even when high contrast is on.
+    expect(resolveThemeName(all, 'paper', highContrast: true), 'paper');
+  });
+}

test/builtin/theme_picker/widget_test.dart

@@ -140,6 +140,23 @@ void main() {
       expect(find.bySemanticsLabel('forest'), findsNothing);
     });
 
+    testWidgets('popover hides -hc rows; the High contrast toggle applies the sibling (T-237)', (tester) async {
+      final f2 = await KernelFixture.create(bundledThemes: [_def('midnight'), _def('midnight-hc')]);
+      addTearDown(f2.dispose);
+      await tester.pumpWidget(harness(f2, const ThemeSwitcherStatusItem()));
+      await tester.pump();
+      await tester.tap(find.bySemanticsLabel('Theme: midnight'));
+      await tester.pumpAndSettle();
+      // Base shown, -hc row hidden, toggle present.
+      expect(find.text('midnight'), findsOneWidget);
+      expect(find.text('midnight-hc'), findsNothing);
+      expect(find.text('High contrast'), findsOneWidget);
+      // Toggling high contrast applies the -hc sibling live.
+      await tester.tap(find.bySemanticsLabel('High contrast'));
+      await tester.pumpAndSettle();
+      expect(f2.services.theme.currentName, 'midnight-hc');
+    });
+
     testWidgets('Esc dismisses the popover without changing the theme (T-234)', (tester) async {
       await tester.pumpWidget(harness(f, const ThemeSwitcherStatusItem()));
       await tester.pump();