feat(android): tap-to-toggle HUD visibility (A1)

On Android, a short tap on the empty game area (not on a card) toggles
the HUD band, info column, and action bar between Visible and Hidden.
Layout recomputes with band_h=0 when hidden so cards fill the full
screen. Any modal open restores the HUD to Visible automatically.

- hud_plugin: HudVisibility resource, HudBand/HudColumn/HudActionBar
  markers, apply_hud_visibility (fires synthetic WindowResized),
  restore_hud_on_modal, and Android-only toggle_hud_on_tap +
  HudTapTracker (15 px slop, skips card taps via DragState.is_idle())
- layout: compute_layout gains hud_visible: bool; passes band_h=0.0
  when hidden; all callers updated
- input_plugin: TouchDragSet (AfterStartDrag / BeforeEndDrag) public
  system-set anchors for cross-plugin ordering
- table_plugin: setup_table + on_window_resized read HudVisibility and
  pass hud_visible to compute_layout
- Desktop behaviour is unchanged (HudVisibility always Visible, tap
  system is #[cfg(target_os = "android")] gated)

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

solitaire_engine/src/cursor_plugin.rs

@@ -604,7 +604,7 @@ mod tests {
         use crate::layout::compute_layout;
 
         let game = GameState::new(42, DrawMode::DrawOne);
-        let layout = compute_layout(Vec2::new(1280.0, 800.0), 0.0, 0.0);
+        let layout = compute_layout(Vec2::new(1280.0, 800.0), 0.0, 0.0, true);
         // A cursor far off-screen should never hit anything.
         assert!(!cursor_over_draggable(Vec2::new(-9999.0, -9999.0), &game, &layout));
     }
@@ -624,7 +624,7 @@ mod tests {
         let mut app = App::new();
         app.add_plugins(MinimalPlugins)
             .insert_resource(GameStateResource(game))
-            .insert_resource(LayoutResource(compute_layout(Vec2::new(1280.0, 800.0), 0.0, 0.0)))
+            .insert_resource(LayoutResource(compute_layout(Vec2::new(1280.0, 800.0), 0.0, 0.0, true)))
             .insert_resource(DragState::default())
             .add_systems(Update, update_drop_target_overlays);
         app