Port weather, copying moves, held items and obedience (#28)

Complete the weather, Substitute, Transform, called-move and forced-switch effects. Add held-item behavior, Exp. Share awards and badge-based traded Pokemon obedience, and persist trainer berry consumption.

Validated with 576 passing unit tests and 149 browser tests, native/reference builds, reference/vendor/release checks and 320 Metal Powder emulator comparisons per browser. Smart AI and special balls/battle types remain on #28.

tests/reference-held-items.spec.ts

@@ -0,0 +1,82 @@
+import { test, expect } from "@playwright/test";
+import { existsSync } from "node:fs";
+import { C } from "../src/game/battle/constants";
+import { romPath, symbolsPath, loadSymbols, openReference } from "./reference-fixture";
+
+test.skip(!existsSync(romPath) || !existsSync(symbolsPath), "Needs the private ROM and pinned reference rebuild.");
+
+test("Metal Powder matches the original species check and byte overflow", async ({ page }) => {
+  const { at, routine } = loadSymbols();
+  const addresses = {
+    command: routine("DittoMetalPowder"),
+    romBank: at("hROMBank"),
+    turn: at("hBattleTurn"),
+    curBattleMon: at("wCurBattleMon"),
+    partySpecies: at("wPartyMon1Species"),
+    enemySpecies: at("wTempEnemyMonSpecies"),
+    playerItem: at("wBattleMonItem"),
+    enemyItem: at("wEnemyMonItem"),
+  };
+  await openReference(page);
+  const differences = await page.evaluate(async ({ addresses, ditto, powder }) => {
+    const { BinjgbEmulator } = await import("/src/emulator/binjgb.ts");
+    const { CrystalAssets } = await import("/src/game/rom/assets.ts");
+    const { Battle } = await import("/src/game/battle/battle.ts");
+    const file = (document.querySelector("#reference-fixture") as HTMLInputElement).files![0];
+    const rom = new Uint8Array(await file.arrayBuffer());
+    const assets = new CrystalAssets(rom);
+    const reference = new BinjgbEmulator();
+    await reference.load(rom, document.createElement("canvas"));
+    const write = (address: number, value: number) => reference.writeMemory(address, value & 255);
+    const read = (address: number) => reference.readMemory(address);
+    const failures: unknown[] = [];
+    let compared = 0;
+    write(0xff70, 1);
+    write(addresses.curBattleMon, 0);
+    for (const turn of [0, 1]) for (const species of [ditto, 25]) for (const item of [powder, 0])
+      for (const attack of [1, 2, 101, 255]) for (const defense of [1, 2, 100, 169, 170, 171, 172, 200, 254, 255]) {
+        const battle = new Battle({
+          data: assets.pokemon, party: [{ species }] as never,
+          pokedex: { seen: new Set(), caught: new Set() },
+          playerId: 1, playerName: "CHRIS", timeOfDay: 1,
+          text: () => ({}) as never, random: () => 0,
+        });
+        const internal = battle as unknown as {
+          enemySpecies: number;
+          dittoMetalPowder(side: unknown, attack: number, defense: number): number[];
+        };
+        internal.enemySpecies = species;
+        const target = turn ? battle.player : battle.enemy;
+        target.mon = { species: 25, item } as never; // transformed battle species
+        const native = internal.dittoMetalPowder(target, attack, defense);
+        write(addresses.turn, turn);
+        write(addresses.partySpecies, species);
+        write(addresses.enemySpecies, species);
+        write(addresses.playerItem, item);
+        write(addresses.enemyItem, item);
+        const { bank, address } = addresses.command;
+        // DI; SP; ROM bank; BC; call the unmodified routine; save B/C;
+        // sentinel in audio RAM (no interrupts); loop.
+        const program = [
+          0xf3, 0x31, 0xfe, 0xc7,
+          0x3e, bank, 0xe0, addresses.romBank & 255, 0xea, 0x00, 0x20,
+          0x06, attack, 0x0e, defense, 0xcd, address & 255, address >> 8,
+          0x78, 0xea, 0xe0, 0xc0, 0x79, 0xea, 0xe1, 0xc0,
+          0x3e, 0x42, 0xea, 0xf0, 0xc0, 0x18, 0xfe,
+        ];
+        write(0xc0f0, 0);
+        program.forEach((byte, i) => write(0xc000 + i, byte));
+        reference.setProgramCounter(0xc000);
+        for (let frame = 0; frame < 60 && read(0xc0f0) !== 0x42; frame++) reference.advanceFrames(1);
+        if (read(0xc0f0) !== 0x42) throw new Error("DittoMetalPowder did not return");
+        const original = [read(0xc0e0), read(0xc0e1)];
+        if (original.some((value, i) => value !== native[i]))
+          failures.push({ turn, species, item, attack, defense, original, native });
+        compared++;
+      }
+    reference.dispose();
+    return { compared, failures };
+  }, { addresses, ditto: C.DITTO, powder: C.METAL_POWDER });
+  expect(differences.compared).toBe(320);
+  expect(differences.failures).toEqual([]);
+});