feat(engine): contextual one-time tips — stall hint, radial menu teach (Phase I)

Two situation-fired teaches, each shown exactly once and recorded in
Settings like shown_achievement_onboarding:

- Stall tip: 45s with no board change in an active, started game
  (clock frozen while paused / a modal is open) points at Hint with
  platform-correct copy (H on desktop, bottom-bar Hint on touch).
- Radial teach: a player 15 moves into a game who has never opened the
  radial menu learns the long-press / right-click gesture. Organic
  radial use marks the tip done silently — nobody is taught what they
  already know.

Tips ride the queued InfoToastEvent path, so they render in the unified
toast stack and never interrupt play. This completes Phase I.

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

solitaire_engine/src/core_game_plugin.rs

@@ -14,14 +14,14 @@ use crate::platform::{
 };
 use crate::{
     AchievementPlugin, AnimationPlugin, AssetSourcesPlugin, AutoCompletePlugin,
-    CardAnimationPlugin, CardPlugin, ChallengePlugin, CursorPlugin, DailyChallengePlugin,
-    DiagnosticsHudPlugin, DifficultyPlugin, FeedbackAnimPlugin, FontPlugin, GamePlugin, HelpPlugin,
-    HomePlugin, HudPlugin, InputPlugin, OnboardingPlugin, PausePlugin, PlayBySeedPlugin,
-    ProfilePlugin, ProgressPlugin, RadialMenuPlugin, ReplayOverlayPlugin, ReplayPlaybackPlugin,
-    SafeAreaInsetsPlugin, SelectionPlugin, SettingsPlugin, SolutionPlaybackPlugin, SplashPlugin,
-    StatsPlugin, SyncProvider, TablePlugin, ThemePlugin, ThemeRegistryPlugin, TimeAttackPlugin,
-    TouchSelectionPlugin, UiFocusPlugin, UiModalPlugin, UiTooltipPlugin, WeeklyGoalsPlugin,
-    WhatsNewPlugin, WinSummaryPlugin,
+    CardAnimationPlugin, CardPlugin, ChallengePlugin, ContextualTipsPlugin, CursorPlugin,
+    DailyChallengePlugin, DiagnosticsHudPlugin, DifficultyPlugin, FeedbackAnimPlugin, FontPlugin,
+    GamePlugin, HelpPlugin, HomePlugin, HudPlugin, InputPlugin, OnboardingPlugin, PausePlugin,
+    PlayBySeedPlugin, ProfilePlugin, ProgressPlugin, RadialMenuPlugin, ReplayOverlayPlugin,
+    ReplayPlaybackPlugin, SafeAreaInsetsPlugin, SelectionPlugin, SettingsPlugin,
+    SolutionPlaybackPlugin, SplashPlugin, StatsPlugin, SyncProvider, TablePlugin, ThemePlugin,
+    ThemeRegistryPlugin, TimeAttackPlugin, TouchSelectionPlugin, UiFocusPlugin, UiModalPlugin,
+    UiTooltipPlugin, WeeklyGoalsPlugin, WhatsNewPlugin, WinSummaryPlugin,
 };
 #[cfg(not(target_arch = "wasm32"))]
 use crate::{
@@ -116,6 +116,7 @@ impl Plugin for CoreGamePlugin {
             .add_plugins(SettingsPlugin::default())
             .add_plugins(OnboardingPlugin)
             .add_plugins(WhatsNewPlugin)
+            .add_plugins(ContextualTipsPlugin)
             .add_plugins(WinSummaryPlugin)
             .add_plugins(UiModalPlugin)
             .add_plugins(UiFocusPlugin)