feat(engine,data): add tap-to-select touch input mode (#70)

- Add TouchInputMode enum (OneTap | TapToSelect) to solitaire_data settings
- Create TouchSelectionPlugin with TouchSelectionState resource and highlight
- Branch handle_double_tap: OneTap → existing auto-move, TapToSelect → two-tap flow
- Add Settings UI toggle row (Touch Input Mode) with TouchInputModeText marker
- Register TouchSelectionPlugin in CoreGamePlugin

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

solitaire_engine/src/lib.rs

@@ -48,6 +48,7 @@ pub mod sync_setup_plugin;
 pub mod table_plugin;
 pub mod theme;
 pub mod time_attack_plugin;
+pub mod touch_selection_plugin;
 pub mod ui_focus;
 pub mod ui_modal;
 pub mod ui_theme;
@@ -142,6 +143,7 @@ pub use safe_area::{SafeAreaAnchoredTop, SafeAreaInsets, SafeAreaInsetsPlugin};
 pub use selection_plugin::{
     KeyboardDragState, SelectionHighlight, SelectionPlugin, SelectionState,
 };
+pub use touch_selection_plugin::{TouchSelectionPlugin, TouchSelectionState};
 pub use settings_plugin::{
     PendingWindowGeometry, SFX_STEP, SettingsChangedEvent, SettingsPlugin, SettingsResource,
     SettingsScreen, WINDOW_GEOMETRY_DEBOUNCE_SECS,