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_spinner.dart

@@ -9,9 +9,9 @@
 /// with bounded pumps.
 library;
 
+import 'package:clide/widgets/src/clide_settings.dart';
 import 'dart:math' as math;
 
-import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/widgets/src/clide_svg_view.dart';
 import 'package:flutter/widgets.dart';
 
@@ -61,7 +61,7 @@ class _ClideSpinnerState extends State<ClideSpinner> with SingleTickerProviderSt
 
   @override
   Widget build(BuildContext context) {
-    final color = widget.color ?? ClideTheme.of(context).surface.globalForeground;
+    final color = widget.color ?? ClideSettings.theme.of(context).surface.globalForeground;
     // Tint every stroke of the multi-colour logo to one colour, keeping alpha.
     final mark = ColorFiltered(
       colorFilter: ColorFilter.mode(color, BlendMode.srcIn),