feat(engine): You hub — Profile/Stats/Achievements/Replays in one tabbed modal

Phase E of docs/ui-redesign-2026-07.md. New you_hub_plugin owns the
modal shell (header, shared tab chips, single Done); each tab's content
is a body builder extracted from its original plugin with every marker
component unchanged, so per-row update/scroll/selector systems keep
working. The replay selector gets its own Replays tab (Watch/Copy
buttons move into the tab body).

- Toggle*RequestEvents + P/S/A accelerators open the hub on the right
  tab, switch tabs in place, or toggle closed on a same-tab request;
  Esc/Done/scrim-click close
- Legacy ProfileScreen/StatsScreen/AchievementsScreen markers ride the
  hub scrim for the active tab — external queries and tests keep their
  meaning
- Standalone toggle/close systems and per-screen Done buttons removed
  (ProfileCloseButton, StatsCloseButton, AchievementsCloseButton)
- Tests: 2 new hub lifecycle tests; profile/stats/achievements modal
  tests adapted (fixtures add YouHubPlugin; selector tests target the
  Replays tab). Engine suite 916 green, clippy -D warnings, fmt.

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

solitaire_engine/src/core_game_plugin.rs

@@ -109,6 +109,7 @@ impl Plugin for CoreGamePlugin {
             .add_plugins(HelpPlugin)
             .add_plugins(HomePlugin::default())
             .add_plugins(ProfilePlugin)
+            .add_plugins(crate::you_hub_plugin::YouHubPlugin)
             .add_plugins(PausePlugin)
             .add_plugins(SettingsPlugin::default())
             .add_plugins(OnboardingPlugin)