refactor(core): make KlondikeInstruction the move currency

Remove the (from, to, count) tuple as an internal move-passing wrapper.
Game logic now stays in KlondikeInstruction space end to end:

- Add GameState::apply_instruction, the native apply path. move_cards
  becomes a thin pile-coordinate adapter that converts to an instruction
  and delegates, so move bookkeeping (validation, score/recycle history,
  undo snapshot) lives in one place instead of being duplicated.
- next_auto_complete_move matches DstFoundation directly instead of
  projecting every candidate to pile coordinates.
- proptests and the storage round-trip test apply instructions directly
  rather than round-tripping instruction -> tuple -> move_cards.

The single instruction -> pile decode is renamed instruction_to_highlight
-> instruction_to_piles and kept in core: decoding a tableau run length
needs upstream pile-stack types core does not re-export, so relocating it
would duplicate the logic across engine and wasm. The two rendering edges
(engine hint highlight, wasm debug move list) call this one decoder; the
engine's hint_piles is a thin delegation to it.

Also includes the CardEntityIndex render-side index and a SelectionPlugin
init_resource fix so update_selection_highlight no longer panics in test
harnesses that omit CardPlugin.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

solitaire_data/src/storage.rs

@@ -506,7 +506,7 @@ mod tests {
     /// will cause at least one pile to disagree.
     #[test]
     fn game_state_v4_mid_game_round_trip() {
-        use solitaire_core::KlondikePile;
+        use solitaire_core::KlondikeInstruction;
         use solitaire_core::game_state::GameState;
 
         let path = gs_path("v4_mid_game");
@@ -524,11 +524,13 @@ mod tests {
 
         // Execute the first available DstTableau or DstFoundation move so the
         // instruction history contains a type other than RotateStock.
-        let moves = gs.possible_instructions();
-        if let Some((from, to, count)) = moves.iter().copied().find(|(_, to, _)| {
-            matches!(to, KlondikePile::Tableau(_) | KlondikePile::Foundation(_))
+        if let Some(instruction) = gs.possible_instructions().into_iter().find(|i| {
+            matches!(
+                i,
+                KlondikeInstruction::DstTableau(_) | KlondikeInstruction::DstFoundation(_)
+            )
         }) {
-            let _ = gs.move_cards(from, to, count);
+            let _ = gs.apply_instruction(instruction);
         }
 
         // Undo once: verifies that `undo_count` is persisted and that the