Port the remaining battle items, the stats screen and hBattleTurn at the menu

- Run every non-ball item effect usable in battle from the ROM's
  ItemEffects: Full Restore, revives, bitter medicine, Bitter Berry, Ethers
  and Elixers, X items, X Accuracy, Guard Spec, Dire Hit and Poké Doll.
- Read happiness changes from HappinessChanges, including the larger
  level-up gain where a Pokémon was caught.
- Model hBattleTurn at the battle menu, including the trainer AI's writes,
  and drop the status-heal refusal.
- Port the stats screen for battles and Bill's PC.
- Compare the send-out and withdraw texts, RestoreHealth, RestorePP,
  ChangeHappiness and CalcPlayerStats with the original routines.

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

tests/pc.test.ts

@@ -226,6 +226,46 @@ describe.skipIf(!existsSync(romPath))("the Pokémon Center PC", () => {
     expect(world.save()).toEqual(saved);
   });
 
+  it("opens the stats screen from Bill's PC for party and boxed Pokémon", () => {
+    const world = fixture();
+    const data = world.assets.pokemon;
+    const pidgey = world.state.party[1];
+    pidgey.hp = 1;
+    pidgey.status = 0x08;
+    open(world);
+    pick(world, "BILL's PC");
+    pick(world, /^DEPOSIT/);
+    pick(world, "PIDGEY");
+    const stats = () => {
+      const choice = world.dialogue?.choice;
+      if (choice?.kind !== "menu") throw new Error("Expected a menu");
+      world.choose(choice.items.indexOf("STATS"));
+      for (let tick = 0; tick < 10 && !world.statsScreen; tick++) world.tick();
+      const shown = world.statsScreen;
+      world.advanceDialogue();
+      until(world);
+      return shown;
+    };
+    // A party Pokémon shows its own HP and status.
+    expect(stats()).toMatchObject({ species: PIDGEY, hp: 1, status: 0x08 });
+    expect(world.statsScreen).toBeUndefined();
+    expect(menuItems(world)).toEqual(["DEPOSIT", "STATS", "RELEASE", "CANCEL"]);
+    pick(world, "DEPOSIT");
+    pick(world, "CANCEL");
+    pick(world, /^WITHDRAW/);
+    pick(world, "PIDGEY");
+    // CalcTempmonStats: a boxed Pokémon shows computed stats, full HP and
+    // no status.
+    const boxed = stats()!;
+    expect(boxed.status).toBe(0);
+    expect(boxed.hp).toBe(boxed.stats[0]);
+    expect(boxed.stats).toEqual(
+      calcStats(data, PIDGEY, pidgey.dvs, 4, pidgey.statExp),
+    );
+    expect(menuItems(world)).toEqual(["WITHDRAW", "STATS", "RELEASE", "CANCEL"]);
+    expect(world.notice, world.diagnostic).toBe("");
+  });
+
   it("refuses to withdraw into a full party or deposit into a full box", () => {
     const world = fixture();
     const party = world.state.party;