remove the dead ColumnHat widget; keep hatHeight (T-385)

ColumnHat was superseded by the hat bar in app.dart and survived only
through a zero-coverage smoke test. Its file also carried the live
hatHeight constant (D-57's 24px hats) consumed by the hat bar and the
menu bar — that moves to widgets/src/chrome_metrics.dart.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/widgets/src/chrome_metrics.dart

@@ -0,0 +1,11 @@
+/// Shared window-chrome metrics.
+///
+/// `hatHeight` used to live in clide_column_hat.dart; the per-column
+/// `ColumnHat` widget there was dead (duplicated by the hat bar in
+/// app.dart, kept alive only by a zero-coverage test) and was removed
+/// in the T-385 sweep — the constant is the part the live chrome
+/// (app.dart hat bar, menu bar) actually consumes (D-57).
+library;
+
+/// Height of the per-column 24px window hats (D-57).
+const double hatHeight = 24;

lib/widgets/src/clide_column_hat.dart

@@ -1,124 +0,0 @@
-import 'dart:io' show Platform;
-
-import 'package:clide/clide.dart' show clideName;
-import 'package:clide/kernel/src/theme/controller.dart';
-import 'package:clide/kernel/src/theme/tokens.dart';
-import 'package:clide/kernel/src/window_controls.dart';
-import 'package:clide/widgets/src/clide_icon.dart';
-import 'package:clide/widgets/src/clide_tappable.dart';
-import 'package:clide/widgets/src/clide_text.dart';
-import 'package:clide/widgets/src/icons/phosphor.dart';
-import 'package:clide/widgets/src/typography.dart';
-import 'package:flutter/foundation.dart' show kIsWeb;
-import 'package:flutter/widgets.dart';
-
-const double hatHeight = 24;
-
-class ColumnHat extends StatelessWidget {
-  const ColumnHat._({required this.position, required this.windowControls, this.projectLabel, this.branchLabel});
-
-  final HatPosition position;
-  final WindowControls windowControls;
-  final String? projectLabel;
-  final String? branchLabel;
-
-  factory ColumnHat.left({required WindowControls windowControls}) => ColumnHat._(position: HatPosition.left, windowControls: windowControls);
-
-  factory ColumnHat.center({required WindowControls windowControls, String? project, String? branch}) =>
-      ColumnHat._(position: HatPosition.center, windowControls: windowControls, projectLabel: project, branchLabel: branch);
-
-  factory ColumnHat.right({required WindowControls windowControls}) => ColumnHat._(position: HatPosition.right, windowControls: windowControls);
-
-  @override
-  Widget build(BuildContext context) {
-    final tokens = ClideTheme.of(context).surface;
-    return GestureDetector(
-      onPanStart: (_) => windowControls.startDrag(),
-      child: Container(
-        height: hatHeight,
-        color: tokens.panelHeader,
-        child: switch (position) {
-          HatPosition.left => _LeftContent(tokens: tokens, wc: windowControls),
-          HatPosition.center => _CenterContent(tokens: tokens, project: projectLabel, branch: branchLabel),
-          HatPosition.right => _RightContent(tokens: tokens, wc: windowControls),
-        },
-      ),
-    );
-  }
-}
-
-enum HatPosition { left, center, right }
-
-class _LeftContent extends StatelessWidget {
-  const _LeftContent({required this.tokens, required this.wc});
-  final SurfaceTokens tokens;
-  final WindowControls wc;
-
-  @override
-  Widget build(BuildContext context) {
-    // On macOS the native titlebar draws traffic lights; skip duplicates.
-    return const SizedBox.expand();
-  }
-}
-
-class _CenterContent extends StatelessWidget {
-  const _CenterContent({required this.tokens, this.project, this.branch});
-  final SurfaceTokens tokens;
-  final String? project;
-  final String? branch;
-
-  @override
-  Widget build(BuildContext context) {
-    final parts = <String>[];
-    if (project != null) parts.add(project!);
-    if (branch != null) parts.add(branch!);
-    final label = parts.isEmpty ? clideName : parts.join(' > ');
-    return Center(
-      child: ClideText(label, fontSize: 12, color: tokens.globalTextMuted, fontFamily: clideMonoFamily),
-    );
-  }
-}
-
-class _RightContent extends StatelessWidget {
-  const _RightContent({required this.tokens, required this.wc});
-  final SurfaceTokens tokens;
-  final WindowControls wc;
-
-  @override
-  Widget build(BuildContext context) {
-    if (kIsWeb) return const SizedBox.expand();
-    final isMac = !kIsWeb && Platform.isMacOS;
-    if (isMac) return const SizedBox.expand();
-    return Row(
-      mainAxisAlignment: MainAxisAlignment.end,
-      children: [
-        _WinButton(icon: const PhosphorIconPainter(0xe32a), onTap: wc.minimize, tokens: tokens),
-        _WinButton(icon: const PhosphorIconPainter(0xe45e), onTap: wc.toggleMaximize, tokens: tokens),
-        _WinButton(icon: PhosphorIcons.byName('x'), onTap: wc.close, tokens: tokens, isClose: true),
-      ],
-    );
-  }
-}
-
-class _WinButton extends StatelessWidget {
-  const _WinButton({required this.icon, required this.onTap, required this.tokens, this.isClose = false});
-  final ClideIconPainter icon;
-  final VoidCallback onTap;
-  final SurfaceTokens tokens;
-  final bool isClose;
-
-  @override
-  Widget build(BuildContext context) {
-    final hoverBg = isClose ? tokens.windowControlCloseHoverBackground : tokens.listItemHoverBackground;
-    return ClideTappable(
-      onTap: onTap,
-      builder: (context, hovered, _) => Container(
-        width: 36,
-        height: hatHeight,
-        color: hovered ? hoverBg : null,
-        alignment: Alignment.center,
-        child: ClideIcon(icon, size: 14, color: hovered && isClose ? tokens.windowControlCloseHoverForeground : tokens.globalTextMuted),
-      ),
-    );
-  }
-}

lib/widgets/widgets.dart

@@ -5,12 +5,12 @@
 /// Flutter chrome widgets directly.
 library;
 
+export 'src/chrome_metrics.dart';
 export 'src/clide_accordion.dart';
 export 'src/clide_anchored.dart';
 export 'src/clide_button.dart';
 export 'src/clide_card_metrics.dart';
 export 'src/clide_collapser_card.dart';
-export 'src/clide_column_hat.dart';
 export 'src/clide_code_block.dart';
 export 'src/clide_divider.dart';
 export 'src/clide_file_image.dart';

test/widgets/zero_coverage_widgets_test.dart

@@ -1,11 +1,10 @@
 /// Smoke + branch tests for the previously-uncovered widgets under
-/// `lib/widgets/src/`: ClidePalette, ClideFilterBox, ColumnHat,
+/// `lib/widgets/src/`: ClidePalette, ClideFilterBox,
 /// ClideIconRail, ClideSpine, ClideResizeBorder.
 library;
 
 import 'package:clide/clide.dart';
 import 'package:clide/extension/extension.dart';
-import 'package:clide/widgets/src/clide_column_hat.dart';
 import 'package:clide/widgets/src/clide_filter_box.dart';
 import 'package:clide/widgets/src/clide_icon.dart';
 import 'package:clide/widgets/src/clide_icon_rail.dart';
@@ -311,41 +310,6 @@ void main() {
     });
   });
 
-  group('ColumnHat', () {
-    late KernelFixture f;
-    setUp(() async => f = await KernelFixture.create());
-    tearDown(() async => f.dispose());
-
-    testWidgets('left / center / right factories render', (tester) async {
-      final wc = WindowControls();
-      addTearDown(wc.dispose);
-      await tester.pumpWidget(
-        harness(
-          f,
-          Column(
-            children: [
-              SizedBox(width: 200, child: ColumnHat.left(windowControls: wc)),
-              SizedBox(
-                width: 200,
-                child: ColumnHat.center(windowControls: wc, project: 'clide', branch: 'main'),
-              ),
-              SizedBox(width: 200, child: ColumnHat.right(windowControls: wc)),
-            ],
-          ),
-        ),
-      );
-      // Center hat renders the joined label.
-      expect(find.text('clide > main'), findsOneWidget);
-    });
-
-    testWidgets('center hat falls back to "clide" with no project/branch', (tester) async {
-      final wc = WindowControls();
-      addTearDown(wc.dispose);
-      await tester.pumpWidget(harness(f, SizedBox(width: 200, child: ColumnHat.center(windowControls: wc))));
-      expect(find.text('clide'), findsOneWidget);
-    });
-  });
-
   group('ClideIconRail', () {
     late KernelFixture f;
     setUp(() async => f = await KernelFixture.create());