feat(engine): tabbed Settings panel — Phase A of the menu redesign

Replaces the 37-row single-scroll settings modal with five tabs
(Audio, Gameplay, Appearance, Accessibility, Account); only the active
tab's rows spawn, so every tab fits without scroll-hunting.

- SettingsTab + ActiveSettingsTab (session-only) + SettingsTabButton
  chips under the modal header; rebuild-on-switch mirrors the
  leaderboard despawn/respawn pattern via a shared build_panel helper
- Accessibility tab gathers color-blind, high-contrast, reduce-motion,
  touch-input, and tooltip-delay from the old Gameplay/Cosmetic mix;
  Account = Sync + Privacy
- SettingsButton enum, input handlers, and persistence untouched
- Tests: per-tab Focusable/Tooltip sweeps, tab-switch rebuild test,
  picker/thumbnail tests pinned to the Appearance tab

Plan: docs/ui-redesign-2026-07.md (also added, phases A–M)

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

solitaire_engine/src/settings_plugin/input.rs

@@ -418,6 +418,25 @@ pub(super) fn handle_settings_buttons(
     }
 }
 
+/// Switches the active Settings tab when a chip is pressed. The
+/// rebuild itself happens in `rebuild_panel_on_tab_change`, driven by
+/// change detection on [`ActiveSettingsTab`].
+pub(super) fn handle_tab_buttons(
+    interactions: Query<(&Interaction, &SettingsTabButton), Changed<Interaction>>,
+    mut active: ResMut<ActiveSettingsTab>,
+) {
+    for (interaction, chip) in &interactions {
+        if *interaction != Interaction::Pressed {
+            continue;
+        }
+        // Compare before writing so re-clicking the active chip doesn't
+        // trip change detection and rebuild the panel for nothing.
+        if active.0 != chip.0 {
+            active.0 = chip.0;
+        }
+    }
+}
+
 /// Handles sync-related settings buttons: Sync Now, Connect, Disconnect,
 /// and Delete Account. Split from `handle_settings_buttons` to stay within
 /// Bevy's 16-parameter system limit.