sweep ClideTappable across 15 files, remove 267 lines

23 StatefulWidget+State hover pairs converted to StatelessWidget
using ClideTappable(builder: (ctx, hovered, _) => ...). Covers
app.dart (5), welcome (2), claude session host (2), column hat (2),
spine (1), pane chrome (1), tab bar (1), decisions (1), tickets (1),
graph (1), pql panel (1), backlinks (1), file tree (2), git panel (1),
git status (1). Only EditorDragHandle and ClidePalette excluded
(drag/keyboard behavior beyond hover+tap).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/widgets/src/clide_pane_chrome.dart

@@ -3,6 +3,7 @@ import 'package:flutter/widgets.dart';
 
 import 'clide_divider.dart';
 import 'clide_icon.dart';
+import 'clide_tappable.dart';
 import 'clide_text.dart';
 import 'icons/x.dart';
 import 'typography.dart';
@@ -67,43 +68,31 @@ class ClidePaneChrome extends StatelessWidget {
   }
 }
 
-class _CloseButton extends StatefulWidget {
+class _CloseButton extends StatelessWidget {
   const _CloseButton({required this.onPressed});
   final VoidCallback onPressed;
 
-  @override
-  State<_CloseButton> createState() => _CloseButtonState();
-}
-
-class _CloseButtonState extends State<_CloseButton> {
-  bool _hover = false;
-
   @override
   Widget build(BuildContext context) {
     final tokens = ClideTheme.of(context).surface;
     return Semantics(
       button: true,
       label: 'Close pane',
-      onTap: widget.onPressed,
-      child: MouseRegion(
-        cursor: SystemMouseCursors.click,
-        onEnter: (_) => setState(() => _hover = true),
-        onExit: (_) => setState(() => _hover = false),
-        child: GestureDetector(
-          behavior: HitTestBehavior.opaque,
-          onTap: widget.onPressed,
-          child: Container(
-            width: 20,
-            height: 20,
-            alignment: Alignment.center,
-            decoration: BoxDecoration(
-              color: _hover ? tokens.tabCloseHover : null,
-            ),
-            child: ClideIcon(
-              const CloseIcon(),
-              size: 10,
-              color: tokens.panelHeaderForeground,
-            ),
+      onTap: onPressed,
+      child: ClideTappable(
+        onTap: onPressed,
+        tooltip: 'Close pane',
+        builder: (context, hovered, _) => Container(
+          width: 20,
+          height: 20,
+          alignment: Alignment.center,
+          decoration: BoxDecoration(
+            color: hovered ? tokens.tabCloseHover : null,
+          ),
+          child: ClideIcon(
+            const CloseIcon(),
+            size: 10,
+            color: tokens.panelHeaderForeground,
           ),
         ),
       ),