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>

src/ui/styles.css

@@ -444,6 +444,89 @@ dialog h2 {
 .battle-menu .wide {
   grid-column: 1 / -1;
 }
+/* The Pokémon stats screen over the battle: three pages, as the pink,
+   green and blue pages of StatsScreenMain. */
+.stats-screen {
+  position: absolute;
+  inset: 0;
+  z-index: 4;
+  display: grid;
+  grid-template-rows: auto 1fr auto;
+  gap: 8px;
+  padding: 10px;
+  overflow-y: auto;
+  color: var(--ink);
+  background: #f8f8f0;
+  border-top: 8px solid var(--stats-page, #e8a0b8);
+}
+.stats-screen[data-page="1"] {
+  --stats-page: #88c888;
+}
+.stats-screen[data-page="2"] {
+  --stats-page: #88a8e0;
+}
+.stats-top {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+}
+.stats-top canvas {
+  width: min(28vw, 112px);
+  aspect-ratio: 1;
+  image-rendering: pixelated;
+}
+.stats-header p,
+.stats-page p {
+  margin: 0;
+  white-space: pre-line;
+}
+.stats-header strong {
+  font-size: 1.1rem;
+}
+.stats-page {
+  display: grid;
+  grid-template-columns: repeat(2, minmax(0, 1fr));
+  gap: 6px 16px;
+  align-content: start;
+  padding: 10px 12px;
+  background: var(--cream);
+  border: 5px double var(--ink);
+  font-variant-numeric: tabular-nums;
+}
+.stats-page dl {
+  display: grid;
+  grid-template-columns: max-content 1fr;
+  gap: 2px 10px;
+  margin: 0;
+}
+.stats-page dt {
+  font-weight: 800;
+}
+.stats-page dd {
+  margin: 0;
+}
+.stats-page .wide {
+  grid-column: 1 / -1;
+}
+.stats-nav {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+.stats-nav button {
+  padding: 6px 12px;
+  color: var(--ink);
+  background: var(--cream-dark);
+  border: 3px double var(--ink);
+}
+.stats-nav #stats-close {
+  margin-left: auto;
+}
+@media (max-width: 480px) {
+  .stats-page {
+    grid-template-columns: minmax(0, 1fr);
+  }
+}
 /* NewGame's screens: a plain background over the world until the
    introduction ends. */
 .intro-screen {