refactor(settings): ClideSettings — one live-preferences facade (D-101)

Introduce ClideSettings, a single widget-facing facade for the app's live
user preferences, namespaced by concern: ClideSettings.fonts.monoOf(context)
/ .fonts.uiOf(context), ClideSettings.theme.of(context),
ClideSettings.i18n.of(context). "Plumb once, use many."

Fonts are carried by a new root-provided ClideSettingsScope (resolved from the
font settings in root_shell, rebuilt on change); theme and i18n delegate to
their existing live providers (ClideTheme / the I18n service) so there's one
source of truth and their many consumers migrate incrementally rather than in
a big-bang. Reads outside a scope fall back to the bundled font defaults, so a
widget renders without a provider (isolated tests).

Migrate ~93 monospace-font call sites across 33 files from the clideMonoFamily
const to ClideSettings.fonts.monoOf(context) — pure refactor, identical family
when no override is set. 11 context-less helper sites (markdown static spans,
a few top-level/static builders) keep the const for now and are tracked in
T-472. Records D-101; updates the ui-design skill's font-family rule.

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

lib/widgets/src/clide_collapser_card.dart

@@ -27,6 +27,7 @@ import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/kernel/src/theme/tokens.dart';
 import 'package:clide/widgets/src/clide_card_metrics.dart';
 import 'package:clide/widgets/src/clide_icon.dart';
+import 'package:clide/widgets/src/clide_settings.dart';
 import 'package:clide/widgets/src/clide_status_indicator.dart';
 import 'package:clide/widgets/src/clide_tappable.dart';
 import 'package:clide/widgets/src/clide_text.dart';
@@ -119,7 +120,7 @@ class _ClideCollapserCardState extends State<ClideCollapserCard> {
         // Chevron — hard against the left edge; the toggle.
         ClideIcon(expanded ? const ChevronDownIcon() : const ChevronRightIcon(), size: 12, color: accent),
         const SizedBox(width: 8),
-        ClideText(widget.label, fontSize: clideFontCaption, fontFamily: clideMonoFamily, color: accent),
+        ClideText(widget.label, fontSize: clideFontCaption, fontFamily: ClideSettings.fonts.monoOf(context), color: accent),
         if (showSummary) ...[
           const SizedBox(width: 10),
           Expanded(
@@ -128,7 +129,7 @@ class _ClideCollapserCardState extends State<ClideCollapserCard> {
               // Summary one step below the label, matching ConversationCard so
               // collapser + tool cards read consistently in the stream (T-344).
               fontSize: clideFontMeta,
-              fontFamily: clideMonoFamily,
+              fontFamily: ClideSettings.fonts.monoOf(context),
               color: tokens.globalTextMuted,
               maxLines: 1,
               overflow: TextOverflow.ellipsis,