refactor(theme): route consumer reads through ClideSettings.theme (T-473)

Migrate ClideTheme.of(context) reads across the widget, feature, and shell
layers to the unified ClideSettings.theme.of(context) facade (D-101), so
theme/i18n/fonts/settings share one widget-facing entry. The facade delegates
straight to ClideTheme, so behaviour is unchanged — goldens are unmoved.

The low-level theme provider keeps its direct ClideTheme.of: the facade is
built on it, and the two kernel sites (ClideTheme's own definition + the
panels drag-resize widget) stay direct to avoid a widgets→kernel import cycle.
Dead controller.dart/kernel.dart imports left by the sweep removed.

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

lib/widgets/src/clide_menu.dart

@@ -8,6 +8,7 @@
 /// quick-open) reuse identical key handling without [ClideMenu]'s rendering.
 library;
 
+import 'package:clide/widgets/src/clide_settings.dart';
 import 'package:clide/kernel/kernel.dart';
 import 'package:clide/widgets/src/clide_icon.dart';
 import 'package:clide/widgets/src/clide_tappable.dart';
@@ -250,7 +251,7 @@ class _ClideMenuState extends State<ClideMenu> {
 
   @override
   Widget build(BuildContext context) {
-    final t = ClideTheme.of(context).surface;
+    final t = ClideSettings.theme.of(context).surface;
     final col = Column(
       mainAxisSize: MainAxisSize.min,
       crossAxisAlignment: CrossAxisAlignment.stretch,