Port Reflect and Light Screen

BattleCommand_Screen and HandleScreens run natively. Each side owns
independent five-turn counters that include the setup turn, do not
refresh on repeated use and survive enemy send-outs. Screens expire in
the original non-Link order with ROM messages; the existing damage path
already doubles the right defense and keeps the critical/stage rule.
This closes the only refusal found by the Route 30 stress run
(Chikorita's Reflect).

The NPC movement test now reads the ROM in beforeAll, so it skips
cleanly without one.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/npc-movement.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from "vitest";
+import { beforeAll, describe, expect, it } from "vitest";
 import { existsSync, readFileSync } from "node:fs";
 import { CrystalAssets } from "../src/game/rom/assets";
 import { GameWorld } from "../src/game/world/world";
@@ -15,7 +15,10 @@ const TEACHER = 4; // 15,11 SPRITEMOVEDATA_WALK_LEFT_RIGHT, radius 1, 0
 const DUDE = 2; // 50,12 SPRITEMOVEDATA_SPINRANDOM_SLOW
 
 describe.skipIf(!existsSync(romPath))("NPC movement with the local ROM", () => {
-  const assets = new CrystalAssets(new Uint8Array(readFileSync(romPath)));
+  let assets: CrystalAssets;
+  beforeAll(() => {
+    assets = new CrystalAssets(new Uint8Array(readFileSync(romPath)));
+  });
   /** A seeded Random so every run takes the same steps. */
   const at = (x: number, y: number, direction: Direction = "down") => {
     let seed = 7;