fix(android): P3 keyboard-hint sweep + clipboard JNI verified

Suppress all remaining keyboard-accelerator chips/labels on Android:
- spawn_modal_button (ui_modal.rs): single cfg gate covers every modal
  across all 13+ callers (onboarding, pause, confirm, game-over, restore,
  play-by-seed, home, help, profile, stats, leaderboard, settings, achievement)
- home_plugin.rs: mode-card hotkey chips (N/C/Z/X/T) gated off
- replay_overlay.rs: [SPACE]/[ESC]/[←→] footer hint text gated off;
  mode-indicator text kept
- help_plugin.rs: kbd chip containers gated off; description text kept

Clipboard JNI verified on Pixel 7 AVD (Android 14): added temporary
KEYCODE_C test hook, logcat confirmed "clipboard JNI OK", hook reverted.
Both JNI bridges (keystore + clipboard) are now confirmed working on device.

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

solitaire_engine/src/help_plugin.rs

@@ -250,9 +250,8 @@ fn spawn_help_screen(commands: &mut Commands, font_res: Option<&FontResource>) {
                         ..default()
                     })
                     .with_children(|line| {
-                        // The hotkey rendered as a small chip with a border —
-                        // visual cue that it's a key reference, not part of
-                        // the description text.
+                        // Keyboard chip — suppressed on Android (no keyboard).
+                        #[cfg(not(target_os = "android"))]
                         line.spawn((
                             Node {
                                 padding: UiRect::axes(VAL_SPACE_2, VAL_SPACE_1),