Finish the opening milestone's switching, items and acceptance run

- Decode evolution lists from the ROM; all 251 match the pinned PRET source.
- Compare CalcMonStats and CalcExpAtLevel against the original routines in
  the reference emulator.
- Add a continuous opening playthrough from the intro to the catching
  tutorial, reloading a JSON save after every stage.
- Port player switching in battle: the PKMN menu, forced choices after a
  faint, Shift mode's offer and double faints, with the original texts.
- Port HP and status healing items in battle through the ROM's ItemEffects,
  HealingHPAmounts and StatusHealingActions tables.
- Add the battle party menu and the Items pocket to the UI.

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

tests/native.test.ts

@@ -12,6 +12,7 @@ import {
   runScript,
 } from "../src/game/scripts/interpreter";
 import { generatePartyMon } from "../src/game/party/pokemon";
+import type { Evolution } from "../src/game/rom/pokemon";
 import { readMovement } from "../src/game/scripts/movement";
 import { defaultTextContext, readText } from "../src/game/scripts/text";
 import { settle, walkTo } from "./world-driver";
@@ -613,6 +614,108 @@ describe.skipIf(!existsSync(romPath))(
           );
       },
     );
+    it("decodes evolution lists, including stat and happiness triggers", () => {
+      const data = load().pokemon;
+      expect(data.evolutions(155)).toEqual([
+        { method: "level", level: 14, species: 156 },
+      ]);
+      expect(data.evolutions(133).map((e) => e.method)).toEqual([
+        "item",
+        "item",
+        "item",
+        "happiness",
+        "happiness",
+      ]);
+      expect(data.evolutions(133)[4]).toEqual({
+        method: "happiness",
+        time: "nite",
+        species: 197,
+      });
+      expect(data.evolutions(61)).toContainEqual({
+        method: "trade",
+        item: 82, // KING'S ROCK
+        species: 186,
+      });
+      expect(data.evolutions(64)).toEqual([
+        { method: "trade", item: null, species: 65 },
+      ]);
+      expect(data.evolutions(236)).toEqual([
+        { method: "stat", level: 20, attack: "lt", species: 107 },
+        { method: "stat", level: 20, attack: "gt", species: 106 },
+        { method: "stat", level: 20, attack: "eq", species: 237 },
+      ]);
+      expect(data.evolutions(251)).toEqual([]);
+      // The four-byte stat records must not shift the learnset.
+      expect(data.learnset(236)[0]).toEqual({ level: 1, move: 33 });
+    });
+    it.skipIf(
+      !existsSync(".reference/pokecrystal/data/pokemon/evos_attacks.asm"),
+    )("matches every evolution list against the pinned PRET source", () => {
+      const data = load().pokemon;
+      const root = ".reference/pokecrystal";
+      const constants = (file: string, first: number) => {
+        const ids = new Map<string, number>();
+        let value = first;
+        for (const line of readFileSync(`${root}/${file}`, "utf8").split(
+          "\n",
+        )) {
+          if (/^DEF NUM_/.test(line)) break;
+          const name = /^\s*const (\w+)/.exec(line)?.[1];
+          if (name) ids.set(name, value++);
+        }
+        return ids;
+      };
+      const species = constants("constants/pokemon_constants.asm", 1),
+        items = constants("constants/item_constants.asm", 0);
+      const id = (map: Map<string, number>, name: string) => {
+        const value = map.get(name);
+        if (value === undefined) throw new Error(`Unknown ${name}`);
+        return value;
+      };
+      const lists: Evolution[][] = [];
+      let current: Evolution[] | null = null;
+      for (const line of readFileSync(
+        `${root}/data/pokemon/evos_attacks.asm`,
+        "utf8",
+      ).split("\n")) {
+        if (/^\w+EvosAttacks:/.test(line)) lists.push((current = []));
+        const args = /^\s*db (EVOLVE_\w+), (.+)$/.exec(line);
+        if (!args || !current) {
+          if (/^\s*db 0 ; no more evolutions/.test(line)) current = null;
+          continue;
+        }
+        const [a, b, c] = args[2].split(",").map((s) => s.trim());
+        if (args[1] === "EVOLVE_LEVEL")
+          current.push({ method: "level", level: +a, species: id(species, b) });
+        else if (args[1] === "EVOLVE_ITEM")
+          current.push({
+            method: "item",
+            item: id(items, a),
+            species: id(species, b),
+          });
+        else if (args[1] === "EVOLVE_TRADE")
+          current.push({
+            method: "trade",
+            item: a === "-1" ? null : id(items, a),
+            species: id(species, b),
+          });
+        else if (args[1] === "EVOLVE_HAPPINESS")
+          current.push({
+            method: "happiness",
+            time: a.slice(3).toLowerCase() as "anytime",
+            species: id(species, b),
+          });
+        else
+          current.push({
+            method: "stat",
+            level: +a,
+            attack: b.slice(4, 6).toLowerCase() as "gt",
+            species: id(species, c),
+          });
+      }
+      expect(lists).toHaveLength(251);
+      lists.forEach((list, i) => expect(data.evolutions(i + 1)).toEqual(list));
+    });
     it("gives the chosen starter and the aide's Potion, then saves them", () => {
       let seed = 7;
       const random = () => (seed = (seed * 73 + 41) & 255);