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>

README.md

@@ -10,13 +10,13 @@ With a Pokémon, head west along Route 29 to Cherrygrove City. Wild Pokémon app
 
 North of Cherrygrove, Route 30's trainers battle you. Bug Catcher Don spots you from a distance and walks over; Youngster Mikey battles when you talk to him. Each sends out two Pokémon, and beaten trainers remember you. The Berry house gives a Berry, and a Potion is hidden on the route.
 
-Mr. Pokémon gives you the Mystery Egg, and Professor Oak gives you the Pokédex. Your rival challenges you in Cherrygrove on the way back, and Elm's aide gives you Poké Balls. Back on Route 29, the Dude shows you how to catch Pokémon. From then on, open PACK in a wild battle to throw a Poké Ball. Caught Pokémon join your party, and you can give them a nickname.
+Mr. Pokémon gives you the Mystery Egg, and Professor Oak gives you the Pokédex. Your rival challenges you in Cherrygrove on the way back, and Elm's aide gives you Poké Balls. Back on Route 29, the Dude shows you how to catch Pokémon. From then on, open PACK in a wild battle to throw a Poké Ball. Caught Pokémon join your party, and you can give them a nickname. In battle, PKMN switches Pokémon, and when one faints you choose the next. PACK's Items pocket uses Potions, Berries and status healers such as Antidote.
 
 Use Start or Select for Key Items, including the Bicycle when owned. The poster opens the Town Map.
 
 The Pokémon Center PC opens Bill's PC, your own PC and, once you have the Pokédex, Professor Oak's rating. Deposit, withdraw and release Pokémon, and switch or name boxes. Store, withdraw or toss items. With six Pokémon in your party, a catch goes to the current box. When that box fills up, Bill calls you. The bedroom PC also lets you arrange owned decorations.
 
-Route 31 and beyond, full party and bag menus, moving Pokémon between boxes, the stats screen, other items in battle and audio are still being ported. Unported neighboring areas appear at the edges but cannot be entered yet.
+Route 31 and beyond, full party and bag menus, moving Pokémon between boxes, the stats screen, battle items such as X Attack or Poké Doll, and audio are still being ported. Unported neighboring areas appear at the edges but cannot be entered yet.
 
 ## Run