fix(engine): platform-correct onboarding copy; Home waits for first-run onboarding (Phase H)

- The how-to-play slide told touch players to left/right-click; Android
  now gets tap/double-tap copy pointing at the bottom-bar Hint button.
- On a fresh profile the Home auto-show spawned underneath the
  onboarding modal, stacking two scrims (v0.44.0 emulator smoke
  finding). spawn_home_on_launch now waits until first_run_complete
  and the onboarding modal is gone, so the launch beat is onboarding,
  then Home, then the table.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_engine/src/onboarding_plugin.rs

@@ -382,20 +382,27 @@ fn spawn_slide_welcome(commands: &mut Commands, font_res: Option<&FontResource>)
     });
 }
 
+/// How-to-play body copy, phrased for the platform's input vocabulary —
+/// a touch player never left-clicks (Phase H polish; spotted in the
+/// emulator smoke of v0.44.0).
+#[cfg(target_os = "android")]
+const HOW_TO_PLAY_BODY: &str = "Drag any face-up card to move it between piles. \
+     You can drag a whole column at once by grabbing the topmost card \
+     you want to move. Double-tap a face-up card to send it to a \
+     foundation pile automatically (when the move is legal). \
+     Tap Hint in the bottom bar for a suggested move.";
+#[cfg(not(target_os = "android"))]
+const HOW_TO_PLAY_BODY: &str = "Left-click and drag any face-up card to move it between piles. \
+     You can drag a whole column at once by grabbing the topmost card \
+     you want to move. Double-click a face-up card to send it to a \
+     foundation pile automatically (when the move is legal). \
+     Right-click a card for a hint — valid destinations will highlight.";
+
 /// Slide 2 — How to play.
 fn spawn_slide_how_to_play(commands: &mut Commands, font_res: Option<&FontResource>) {
     spawn_modal(commands, OnboardingScreen, Z_ONBOARDING, |card| {
         spawn_modal_header(card, "Drag cards to play", font_res);
-        spawn_modal_body_text(
-            card,
-            "Left-click and drag any face-up card to move it between piles. \
-             You can drag a whole column at once by grabbing the topmost card \
-             you want to move. Double-click a face-up card to send it to a \
-             foundation pile automatically (when the move is legal). \
-             Right-click a card for a hint — valid destinations will highlight.",
-            TEXT_SECONDARY,
-            font_res,
-        );
+        spawn_modal_body_text(card, HOW_TO_PLAY_BODY, TEXT_SECONDARY, font_res);
         spawn_modal_actions(card, |actions| {
             spawn_modal_button(
                 actions,