feat(slay-the-spire-like): support source entity in effect targeting

Update `getEffectTargets` to accept a `sourceEntityKey`. This allows
"self" targets to correctly resolve to the entity triggering the
effect (e.g., a player or a specific enemy) rather than defaulting
to a hardcoded player reference.

src/samples/slay-the-spire-like/system/combat/effects.ts

@@ -107,12 +107,16 @@ export function* getEffectTargets(
   target: CardEffectTarget | EffectTarget,
   game: CombatGameContext,
   targetId?: string,
+  sourceEntityKey: "player" | string = "player",
 ) {
   if (target === "all" || target === "team") {
     for (const enemy of getAliveEnemies(game.value)) {
       yield enemy;
     }
   } else if (target === "self") {
+    const entity = getCombatEntity(game.value, sourceEntityKey);
+    if (entity) yield entity;
+  } else if (target === "player") {
     yield game.value.player;
   } else if (target === "target") {
     if (!targetId) return;