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>

tests/battle-switch.test.ts

@@ -183,6 +183,18 @@ describe.skipIf(!existsSync(romPath))("switching Pokémon in battle", () => {
     expect(texts).toContain("YOUNGSTER MIKEY was defeated!");
   });
 
+  it("makes no offer in Set mode", () => {
+    const battle = new Battle({
+      ...options([mon(CYNDAQUIL, 15), mon(TOTODILE, 15)], { trainer: [22, 2] }),
+      shift: false,
+    });
+    const { texts } = play(battle, {});
+    expect(texts).toContain("YOUNGSTER MIKEY sent out RATTATA!");
+    expect(texts.some((text) => text.includes("is about to use"))).toBe(false);
+    expect(texts.some((text) => text.includes("change POKéMON"))).toBe(false);
+    expect(texts).toContain("YOUNGSTER MIKEY was defeated!");
+  });
+
   it("keeps the Pokémon in when the offer is declined", () => {
     const battle = new Battle(
       options([mon(CYNDAQUIL, 15), mon(TOTODILE, 15)], { trainer: [22, 2] }),