fix(engine): silence Android-target dead-code and unused-import warnings

All 10 warnings were caused by hotkey/keyboard UI code behind
#[cfg(not(target_os = "android"))] call sites whose definitions lacked
the matching gate. Fixes:
- help_plugin: gate keyboard-chip imports and font_kbd; #[allow(dead_code)]
  on ControlRow (keys field is data, not dead)
- hud_plugin/ui_modal: replace cfg shadow pattern with cfg!() expression
  so the hotkey parameter is read on every platform
- home_plugin: gate fn hotkey behind not(android)
- onboarding_plugin: gate HotkeyRow, HOTKEYS, spawn_slide_hotkeys and
  their exclusive imports behind not(android)
- replay_overlay: gate keybind_footer_hint_text behind not(android)

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

solitaire_engine/src/help_plugin.rs

@@ -13,10 +13,9 @@ use crate::ui_modal::{
     spawn_modal, spawn_modal_actions, spawn_modal_button, spawn_modal_header, ButtonVariant,
     ScrimDismissible,
 };
-use crate::ui_theme::{
-    BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, SPACE_2, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY,
-    TYPE_CAPTION, VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3, Z_MODAL_PANEL,
-};
+use crate::ui_theme::{SPACE_2, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, VAL_SPACE_2, VAL_SPACE_3, Z_MODAL_PANEL};
+#[cfg(not(target_os = "android"))]
+use crate::ui_theme::{BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, TYPE_CAPTION, VAL_SPACE_1};
 
 /// Marker on the help overlay root node.
 #[derive(Component, Debug)]
@@ -123,6 +122,7 @@ fn scroll_help_panel(
 }
 
 /// Each entry in the controls reference table.
+#[allow(dead_code)]
 struct ControlRow {
     keys: &'static str,
     description: &'static str,
@@ -243,6 +243,7 @@ fn spawn_help_screen(commands: &mut Commands, font_res: Option<&FontResource>) {
         ..default()
     };
     let font_row = font_section.clone();
+    #[cfg(not(target_os = "android"))]
     let font_kbd = TextFont {
         font: font_handle,
         font_size: TYPE_CAPTION,

solitaire_engine/src/home_plugin.rs

@@ -174,6 +174,7 @@ impl HomeMode {
 
     /// The keyboard accelerator that dispatches the same launch event,
     /// shown in a small chip on the card.
+    #[cfg(not(target_os = "android"))]
     fn hotkey(self) -> &'static str {
         match self {
             HomeMode::Classic => "N",

solitaire_engine/src/hud_plugin.rs

@@ -799,8 +799,7 @@ fn spawn_action_button<M: Component>(
     // visibly clutter the narrow-viewport action row. Force the hint
     // off on Android; the chevrons on Menu/Modes remain because they
     // indicate dropdown behaviour and still apply on touch.
-    #[cfg(target_os = "android")]
-    let hotkey: Option<&'static str> = None;
+    let hotkey = if cfg!(target_os = "android") { None } else { hotkey };
 
     let hotkey_font = TextFont {
         font: font.font.clone(),

solitaire_engine/src/onboarding_plugin.rs

@@ -31,9 +31,11 @@ use crate::ui_modal::{
     spawn_modal, spawn_modal_actions, spawn_modal_body_text, spawn_modal_button,
     spawn_modal_header, ButtonVariant,
 };
+use crate::ui_theme::{TEXT_SECONDARY, Z_ONBOARDING};
+#[cfg(not(target_os = "android"))]
 use crate::ui_theme::{
-    BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY,
-    TYPE_CAPTION, VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3, Z_ONBOARDING,
+    BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, TEXT_PRIMARY, TYPE_BODY, TYPE_CAPTION,
+    VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3,
 };
 
 // ---------------------------------------------------------------------------
@@ -86,6 +88,7 @@ pub struct OnboardingSlideIndex(pub u8);
 // ---------------------------------------------------------------------------
 
 /// A single `key — description` pair shown on slide 3.
+#[cfg(not(target_os = "android"))]
 struct HotkeyRow {
     keys: &'static str,
     description: &'static str,
@@ -96,6 +99,7 @@ struct HotkeyRow {
 /// Updating the list in `help_plugin.rs` should be mirrored here. The
 /// ARCHITECTURE.md decision log calls out that we copy values rather than
 /// refactor the help plugin.
+#[cfg(not(target_os = "android"))]
 const HOTKEYS: &[HotkeyRow] = &[
     HotkeyRow { keys: "D / Space", description: "Draw from stock" },
     HotkeyRow { keys: "U", description: "Undo last move" },
@@ -359,6 +363,7 @@ fn spawn_slide_how_to_play(commands: &mut Commands, font_res: Option<&FontResour
 }
 
 /// Slide 3 — Keyboard shortcuts.
+#[cfg(not(target_os = "android"))]
 fn spawn_slide_hotkeys(commands: &mut Commands, font_res: Option<&FontResource>) {
     let font_handle = font_res.map(|f| f.0.clone()).unwrap_or_default();
     let font_row = TextFont {

solitaire_engine/src/replay_overlay.rs

@@ -1165,6 +1165,7 @@ fn keybind_footer_mode_text() -> &'static str {
 /// pause/resume, the ESC accelerator for stop, and the ← / →
 /// accelerators for paused single-move stepping. The footer never
 /// lists unimplemented keybinds (would lie to users).
+#[cfg(not(target_os = "android"))]
 fn keybind_footer_hint_text() -> &'static str {
     "[SPACE] pause/resume \u{00B7} [ESC] stop \u{00B7} [\u{2190}\u{2192}] step" // · separator
 }

solitaire_engine/src/ui_modal.rs

@@ -335,8 +335,7 @@ pub fn spawn_modal_button<M: Component>(
     variant: ButtonVariant,
     font_res: Option<&FontResource>,
 ) {
-    #[cfg(target_os = "android")]
-    let hotkey: Option<&'static str> = None;
+    let hotkey = if cfg!(target_os = "android") { None } else { hotkey };
     let font_handle = font_res.map(|f| f.0.clone()).unwrap_or_default();
     let font_label = TextFont {
         font: font_handle.clone(),