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/battle-driver.ts

@@ -66,8 +66,8 @@ export function battleOptions(
 }
 
 /** Run a battle. Menus take queued answers per prompt kind, then the
- * defaults: the first move, YES, cancelling a move to forget and the
- * first party slot. */
+ * defaults: the first move, YES, cancelling a move to forget, and the
+ * first party slot or move slot. */
 export function playBattle(
   battle: Battle,
   queued: Partial<Record<BattleEffect["kind"], BattleInput[]>> = {},
@@ -94,10 +94,43 @@ export function playBattle(
               ? 1
               : effect.kind === "forget"
                 ? 4
-                : effect.kind === "party"
+                : effect.kind === "party" || effect.kind === "move"
                   ? 0
                   : undefined;
     }
   }
   throw new Error("Battle did not end.");
 }
+
+/** Step a battle by hand: texts are collected up to each prompt, and
+ * `answer` feeds the current prompt's input. */
+export function battleSteps(battle: Battle) {
+  const run = battle.run();
+  const texts: string[] = [];
+  let next = run.next();
+  const collect = () => {
+    while (
+      !next.done &&
+      (next.value.kind === "text" || next.value.kind === "hud")
+    ) {
+      if (next.value.kind === "text")
+        texts.push(next.value.text.replace(/\n/g, " "));
+      next = run.next();
+    }
+  };
+  collect();
+  return {
+    texts,
+    get prompt(): BattleEffect | undefined {
+      return next.done ? undefined : next.value;
+    },
+    get done() {
+      return Boolean(next.done);
+    },
+    answer(input: BattleInput) {
+      next = run.next(input);
+      collect();
+      return this;
+    },
+  };
+}