fix(engine): Android HUD QA — glyph, avatar, toggle, modal-dismiss safety

Bug A: Replace U+21C4 (tofu on FiraMono) with plain ASCII "M" on the
Modes action button.

Bug B: HudAvatar disc was invisible against BG_HUD_BAND (same dark
grey). Switch background to ACCENT_PRIMARY and text to TEXT_PRIMARY so
the disc is clearly visible.

Bug C/D: toggle_hud_on_tap improvements:
- Drain buffered TouchInput events in the early-return path (scrim
  present or paused) so the modal-dismiss frame does not replay the
  button tap's Started+Ended pair as a spurious toggle.
- Stop clearing start_pos on TouchPhase::Moved — Android fires Moved
  even for clean taps (jitter), and the distance check at Ended already
  rejects real drags via drag.is_idle(). Clearing it silently swallowed
  toggle attempts on physical devices.
- Increase HUD_TAP_SLOP_PX from 15 → 25 for better tap recognition.

Also reduces Android HUD_BAND_HEIGHT from 128 → 80 px now that action
buttons live in the bottom bar rather than the top band.

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

solitaire_engine/src/safe_area.rs

@@ -51,12 +51,25 @@ pub struct SafeAreaAnchoredTop {
     pub base_top: f32,
 }
 
+/// Marker for `Node` entities whose `bottom` offset should be re-applied
+/// as `base_bottom + SafeAreaInsets::bottom / scale`.
+///
+/// Use this for elements anchored to the bottom edge (e.g. a bottom action
+/// bar) so they clear the Android gesture-navigation zone automatically.
+#[derive(Component, Debug, Clone, Copy)]
+pub struct SafeAreaAnchoredBottom {
+    pub base_bottom: f32,
+}
+
 pub struct SafeAreaInsetsPlugin;
 
 impl Plugin for SafeAreaInsetsPlugin {
     fn build(&self, app: &mut App) {
         app.init_resource::<SafeAreaInsets>()
-            .add_systems(Update, (apply_safe_area_anchors, apply_safe_area_to_modal_scrims));
+            .add_systems(
+                Update,
+                (apply_safe_area_anchors, apply_safe_area_bottom_anchors, apply_safe_area_to_modal_scrims),
+            );
 
         #[cfg(target_os = "android")]
         app.add_systems(Update, android::refresh_insets);
@@ -89,6 +102,23 @@ fn apply_safe_area_anchors(
     }
 }
 
+/// Re-applies `base_bottom + insets.bottom / scale` to every entity carrying
+/// [`SafeAreaAnchoredBottom`] whenever [`SafeAreaInsets`] changes.
+fn apply_safe_area_bottom_anchors(
+    insets: Res<SafeAreaInsets>,
+    windows: Query<&Window>,
+    mut q: Query<(&SafeAreaAnchoredBottom, &mut Node)>,
+) {
+    if !insets.is_changed() {
+        return;
+    }
+    let scale = windows.iter().next().map_or(1.0, |w| w.scale_factor());
+    let bottom_logical = insets.bottom / scale;
+    for (anchor, mut node) in &mut q {
+        node.bottom = Val::Px(anchor.base_bottom + bottom_logical);
+    }
+}
+
 /// Pads the bottom of every [`ModalScrim`] by the logical bottom inset so
 /// modal cards don't extend into the Android gesture-navigation zone.
 ///