feat(engine): Phase B home hierarchy — Continue card, hero New Game, deal-options disclosure

Restructures the Home overlay per docs/ui-redesign-2026-07.md Phase B:

- Continue card (mode / elapsed / score) when a game is in progress;
  clicking returns to the table
- Hero New Game replays the persisted Settings::last_mode (new field,
  serde-default Classic) with one tap; locked modes fall back to Classic
- Deal options (draw 1/3, winnable-only, difficulty tiers) move into a
  disclosure under the hero — off the Home top level (decision 2)
- Compact symmetric 2x3 mode grid; descriptions on wide viewports only
- Stats strip moves to the bottom (right pane on wide)
- Two-pane body on wide viewports (>= 1000 logical px) via new
  ui_modal::spawn_modal_sized (default card stays 720 px)
- Cancel becomes "Back to table" and only renders while a live
  (un-won) game exists

10 new home_plugin tests; all 936 engine tests + clippy green.

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

solitaire_engine/src/ui_modal.rs

@@ -178,6 +178,26 @@ pub fn spawn_modal<M: Component, F>(
     z_panel: i32,
     build_card: F,
 ) -> Entity
+where
+    F: FnOnce(&mut ChildSpawnerCommands),
+{
+    spawn_modal_sized(commands, plugin_marker, z_panel, MODAL_CARD_MAX_WIDTH, build_card)
+}
+
+/// Default maximum card width in logical pixels — every [`spawn_modal`]
+/// caller gets this. Surfaces that lay out side-by-side panes (e.g. the
+/// two-pane Home on wide viewports) can raise it via [`spawn_modal_sized`].
+pub const MODAL_CARD_MAX_WIDTH: f32 = 720.0;
+
+/// [`spawn_modal`] with an explicit card `max_width`. Behaviour is
+/// otherwise identical — same scrim, enter animation, and card chrome.
+pub fn spawn_modal_sized<M: Component, F>(
+    commands: &mut Commands,
+    plugin_marker: M,
+    z_panel: i32,
+    max_width: f32,
+    build_card: F,
+) -> Entity
 where
     F: FnOnce(&mut ChildSpawnerCommands),
 {
@@ -235,7 +255,7 @@ where
                     padding: UiRect::all(VAL_SPACE_5),
                     border: UiRect::all(Val::Px(1.0)),
                     border_radius: BorderRadius::all(Val::Px(RADIUS_LG)),
-                    max_width: Val::Px(720.0),
+                    max_width: Val::Px(max_width),
                     align_items: AlignItems::Stretch,
                     ..default()
                 },