fix(android): replace non-FiraMono HUD glyphs with safe Unicode alternatives

⏸ (U+23F8), ★ (U+2605), ⚙ (U+2699) are absent from FiraMono and rendered
as boxes on device. Replace with ← ‖ → ▾ which all fall within FiraMono's
covered blocks (Basic Latin + Arrows + General Punctuation + Geometric Shapes).

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

solitaire_engine/src/hud_plugin.rs

@@ -626,11 +626,16 @@ fn spawn_action_buttons(
     mut commands: Commands,
 ) {
     let top_inset = insets.as_deref().copied().unwrap_or_default().top;
+    #[cfg(not(target_os = "android"))]
     let font = TextFont {
         font: font_res.as_ref().map(|f| f.0.clone()).unwrap_or_default(),
         font_size: TYPE_BODY,
         ..default()
     };
+    // Android labels use only FiraMono-safe glyphs (≡ ← ‖ → ▾), so the same
+    // embedded font works — no system font fallback required.
+    #[cfg(target_os = "android")]
+    let font = TextFont { font_size: TYPE_BODY, ..default() };
 
     // On Android, 7 text-labelled buttons at 48 dp each wrap to two rows on
     // a 411 dp phone. Use compact Unicode symbols and tighter gaps so all 7
@@ -645,12 +650,12 @@ fn spawn_action_buttons(
 
     #[cfg(target_os = "android")]
     let labels = (
-        /* menu */  "\u{2261}",          // ≡  hamburger
-        /* undo */  "\u{21A9}",          // ↩  undo arrow
-        /* pause */ "\u{23F8}",          // ⏸  pause symbol
+        /* menu */  "\u{2261}",  // ≡  identical-to (hamburger look-alike, in FiraMono)
+        /* undo */  "\u{2190}",  // ←  leftwards arrow (in FiraMono)
+        /* pause */ "\u{2016}",  // ‖  double vertical line (in FiraMono general-punct)
         /* help */  "?",
-        /* hint */  "\u{2605}",          // ★  star
-        /* modes */ "\u{2699}\u{25BE}",  // ⚙▾ gear+chevron
+        /* hint */  "\u{2192}",  // →  rightwards arrow (in FiraMono)
+        /* modes */ "\u{25BE}",  // ▾  small down-pointing triangle (in FiraMono)
         /* new */   "+",
     );
     #[cfg(not(target_os = "android"))]