Port the options screen

OPTION in the start menu runs _Option with the ROM's labels and settings,
OptionsControl's cursor wrapping and each option's bit handling. The four
option bytes live in the script state and saves, defaulting to
DefaultOptions. The battle style now decides whether a trainer's next
Pokémon brings an offer to switch, and the menu account whether the start
menu describes its items; the other settings are kept for later.

Closes #24

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/game/battle/battle.ts

@@ -182,6 +182,8 @@ export interface BattleOptions {
   /** wMomSavingMoney's MOM_SAVING_MONEY_MASK bits and wMomsMoney: how much
    * of a trainer's prize goes to Mom. */
   mom?: { saving: number; money: number };
+  /** wOptions' BATTLE_SHIFT clear: the SHIFT battle style (the default). */
+  shift?: boolean;
 }
 
 /** BATTLERESULT_BOX_FULL: a catch filled the current box. */
@@ -2954,11 +2956,12 @@ export class Battle {
     this.curOTMon = index;
     this.loadEnemyMon();
   }
-  /** CheckWhetherToAskSwitch: Shift mode (the only battle style so far)
-   * asks when the player has another Pokémon and its own is still up. */
+  /** CheckWhetherToAskSwitch: the SHIFT battle style asks when the player
+   * has another Pokémon and its own is still up. */
   private checkWhetherToAskSwitch() {
     return (
       !this.battleHasJustStarted &&
+      this.options.shift !== false &&
       this.options.party.length > 1 &&
       this.partyMon.hp > 0
     );