fix(engine): raise dynamic tableau fan cap to fill tall viewports

MAX_DYNAMIC_FAN_FRAC 0.6 -> 0.9 so the dynamic tableau fill spreads
further on very tall / narrow viewports (e.g. a foldable cover screen),
which were left ~40% empty at the cap. Fills the unfolded near-square
screen to ~100% and lets the cover screen fill further (and the rest fills
as columns deepen during play). Normal phones are unaffected — their fill
fraction is already below the cap. apply_dynamic_tableau_fan still floors
at TABLEAU_FAN_FRAC and deeper columns drive the fraction down, so nothing
overflows and hit-testing stays in sync.

Vertical centring of the residual was investigated but dropped: a 21:9
phone is aspect-identical to the cover screen, so centring can't be
targeted to foldables without also disconnecting the board from the HUD on
tall phones.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -41,7 +41,9 @@ project follows [Semantic Versioning](https://semver.org/).
   each column's total depth (face-down cards included) and refills on the
   cold-start deal, every move, and on resize (incl. the Android safe-area-inset
   resize and fold/unfold), so a near-square viewport such as an unfolded Galaxy
-  Fold no longer leaves the bottom of the screen empty.
+  Fold no longer leaves the bottom of the screen empty. The fan spread cap was
+  raised so very tall / narrow viewports (e.g. a foldable cover screen) fill
+  further.
 - **Card-move animation jank.** A move now rebuilds a card's child visuals only
   when its appearance changes (flip / resize / accessibility) instead of
   despawning and respawning every card's children each `StateChangedEvent`,

solitaire_engine/src/layout.rs

@@ -99,7 +99,7 @@ const MAX_TABLEAU_CARDS: f32 = 13.0;
 /// clear overlap (a readable stack) while still filling most of a near-square /
 /// unfolded-foldable screen. Tunable purely for feel — no effect on correctness
 /// or hit-testing.
-pub(crate) const MAX_DYNAMIC_FAN_FRAC: f32 = 0.6;
+pub(crate) const MAX_DYNAMIC_FAN_FRAC: f32 = 0.9;
 
 /// Vertical pixel band reserved at the top of the play area for the HUD
 /// (action buttons, Score / Moves / Timer readouts). The card grid starts
@@ -285,13 +285,12 @@ pub fn compute_layout(
         );
     }
 
-    // Adaptive tableau fan fraction. On height-limited (desktop) windows the
+    // Adaptive tableau fan fraction. On height-limited windows the height-based
-    // height-based sizing already ensures a worst-case 13-card column fits at
+    // sizing already ensures a worst-case 13-card column fits at TABLEAU_FAN_FRAC,
-    // TABLEAU_FAN_FRAC (0.25), so the formula returns ≈0.25 and the clamp
+    // so the formula returns the minimum and the clamp keeps it there. On
-    // keeps it there — no change from prior behaviour. On width-limited
+    // width-limited (portrait phone) windows card_size is small and lots of
-    // (portrait phone) windows card_size is small and lots of vertical space
+    // vertical space is unused; solve for the fraction that fills the available
-    // is unused; we solve for the fraction that exactly fills the available
+    // space. `apply_dynamic_tableau_fan` later refines this for the actual deal.
-    // space to the bottom margin.
     //
     // avail = distance from the top of the first tableau card to the bottom
     //         margin — i.e. the space available for 12 fan steps.
@@ -302,20 +301,17 @@ pub fn compute_layout(
     } else {
         TABLEAU_FAN_FRAC
     };
-    // Never go below the desktop minimum — avoids shrinking the fan on
-    // degenerate near-square windows where the formula might undershoot.
     let tableau_fan_frac = ideal_fan_frac.max(TABLEAU_FAN_FRAC);
-    // Scale the face-down fraction proportionally so rendering and hit-testing
-    // stay in sync (TABLEAU_FACEDOWN_FAN_FRAC / TABLEAU_FAN_FRAC = 0.48 ratio).
     let facedown_scale = TABLEAU_FACEDOWN_FAN_FRAC / TABLEAU_FAN_FRAC;
     let tableau_facedown_fan_frac = tableau_fan_frac * facedown_scale;
+    let available_tableau_height = avail;
 
     Layout {
         card_size,
         pile_positions,
         tableau_fan_frac,
         tableau_facedown_fan_frac,
-        available_tableau_height: avail,
+        available_tableau_height,
     }
 }