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/home_plugin.rs

@@ -1385,8 +1385,8 @@ fn spawn_mode_card(
                 ));
 
                 if unlocked {
-                    // Hotkey chip — same look as the kbd-chip rows used
-                    // elsewhere so accelerators read consistently.
+                    // Hotkey chip — suppressed on Android (touch builds have no keyboard).
+                    #[cfg(not(target_os = "android"))]
                     row.spawn((
                         Node {
                             padding: UiRect::axes(VAL_SPACE_2, VAL_SPACE_1),