feat(engine): Android UX sweep — tap-to-move, safe area, HUD polish

Single-tap auto-move (input_plugin):
- Remove 0.5 s double-tap window; any uncommitted TouchPhase::Ended on
  a face-up card now fires MoveRequestEvent immediately.

Bottom safe-area inset (layout, table_plugin):
- compute_layout gains safe_area_bottom param; height budget and bottom
  margin both respect the navigation bar reservation.

Card back contrast (card_plugin):
- CardBackFrame child sprite (gray, card_size + 3 px, local z=-0.01)
  spawned behind every face-down card so the dark back_0.png reads as
  a distinct rectangle against the dark felt.

HUD action bar compactness (hud_plugin):
- max_width 50% → 65% on the action button row; 6 buttons now wrap to
  2 rows instead of 3 on a 360 dp phone.

Dynamic tableau fan fraction (layout, card_plugin):
- Layout gains available_tableau_height field.
- update_tableau_fan_frac system (after GameMutation, before
  sync_cards_on_change) grows face-up fan from 0.25 to the window max
  as revealed column depth increases. Face-down fan is left at the
  window-adaptive value so stacks stay visible.

ModesPopover + MenuPopover light-dismiss (hud_plugin):
- Fullscreen transparent Button backdrop spawned at Z_HUD+4 behind each
  popover; tapping outside the panel despawns both panel and backdrop.

Stock badge legibility (card_plugin):
- Badge font TYPE_CAPTION (11 pt) → TYPE_BODY (14 pt); background
  sprite 28×16 → 34×20 world units.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_engine/src/radial_menu.rs

@@ -801,7 +801,7 @@ mod tests {
 
     fn install_resources(app: &mut App, state: GameState, layout_window: Vec2, cursor: Vec2) {
         app.insert_resource(GameStateResource(state));
-        app.insert_resource(LayoutResource(compute_layout(layout_window, 0.0)));
+        app.insert_resource(LayoutResource(compute_layout(layout_window, 0.0, 0.0)));
         app.world_mut().resource_mut::<RadialCursorOverride>().0 = Some(cursor);
     }
 
@@ -913,7 +913,7 @@ mod tests {
     fn right_click_press_on_face_up_card_opens_radial() {
         let mut app = radial_test_app();
         let layout_window = Vec2::new(1280.0, 800.0);
-        let layout = compute_layout(layout_window, 0.0);
+        let layout = compute_layout(layout_window, 0.0, 0.0);
         let ace_pos = layout.pile_positions[&PileType::Tableau(0)];
 
         install_resources(&mut app, ace_only_state(), layout_window, ace_pos);
@@ -950,7 +950,7 @@ mod tests {
     fn right_click_release_over_destination_fires_move_request() {
         let mut app = radial_test_app();
         let layout_window = Vec2::new(1280.0, 800.0);
-        let layout = compute_layout(layout_window, 0.0);
+        let layout = compute_layout(layout_window, 0.0, 0.0);
         let ace_pos = layout.pile_positions[&PileType::Tableau(0)];
 
         install_resources(&mut app, ace_only_state(), layout_window, ace_pos);
@@ -989,7 +989,7 @@ mod tests {
     fn right_click_release_outside_any_destination_cancels() {
         let mut app = radial_test_app();
         let layout_window = Vec2::new(1280.0, 800.0);
-        let layout = compute_layout(layout_window, 0.0);
+        let layout = compute_layout(layout_window, 0.0, 0.0);
         let ace_pos = layout.pile_positions[&PileType::Tableau(0)];
 
         install_resources(&mut app, ace_only_state(), layout_window, ace_pos);
@@ -1016,7 +1016,7 @@ mod tests {
     fn escape_cancels_active_radial() {
         let mut app = radial_test_app();
         let layout_window = Vec2::new(1280.0, 800.0);
-        let layout = compute_layout(layout_window, 0.0);
+        let layout = compute_layout(layout_window, 0.0, 0.0);
         let ace_pos = layout.pile_positions[&PileType::Tableau(0)];
 
         install_resources(&mut app, ace_only_state(), layout_window, ace_pos);
@@ -1039,7 +1039,7 @@ mod tests {
     fn right_click_on_face_down_card_does_not_open_radial() {
         let mut app = radial_test_app();
         let layout_window = Vec2::new(1280.0, 800.0);
-        let layout = compute_layout(layout_window, 0.0);
+        let layout = compute_layout(layout_window, 0.0, 0.0);
         let king_pos = layout.pile_positions[&PileType::Tableau(0)];
 
         install_resources(&mut app, face_down_only_state(), layout_window, king_pos);