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>

docs/PLAN.md

@@ -144,11 +144,23 @@ The numbered sections below keep their full scope. Each one opens with a checkli
 - Save format 3 gained `intro` and `clock.minuteOffset`, migrated by absence to a finished intro on the device clock.
 - Intentional change: the steppers start at the device's current time rather than 10:00, so confirming keeps the device clock.
 - Not presented: the palette fades, Wooper's cry, the picture slide during name selection, `ShrinkPlayer` and the Route 30 music (no audio yet).
-- Next: player switching and other items in battle; MOVE PKMN W/O MAIL and the stats screen with the party menu; a continuous opening playthrough.
+- Next: MOVE PKMN W/O MAIL and the stats screen with the party menu.
+
+## Implemented: evolution data, reference vectors and the opening playthrough
+
+- `PokemonData.evolutions` decodes the evolution list before each learnset: level, item, trade (with or without a held item), happiness by time of day, and Tyrogue's four-byte stat records. All 251 lists match the pinned PRET source. Evolving itself is not ported yet.
+- The reference suite also runs the original `CalcMonStats` (300 cases, with and without stat experience, including levels above 100 that reach the 999 cap) and `CalcExpAtLevel` (every growth rate at levels 1–100).
+- `tests/playthrough.test.ts` plays a new game from the introduction to the catching tutorial with a seeded RNG: Mom, Elm, the starter and Potion, Route 29, Cherrygrove, Route 30, Mr. Pokémon, Elm's call, the rival battle, the officer, the Egg, the aide's Poké Balls and the Dude's demonstration. Wild battles are fought, or fled below half HP. Each stage ends with a JSON save loaded into a fresh world. It uses no fixtures or hand-set flags, but drives `GameWorld` directly rather than the browser UI.
+
+## Implemented: switching and healing items in battle
+
+- PKMN opens the party menu; SWITCH sends out the chosen Pokémon (STATS is not ported). The texts, the trapped and fainted checks, and the enemy's turn after the switch follow the original. Both Pokémon share the experience.
+- After a faint, wild battles ask "Use next POKéMON?" (NO tries to run) and the party menu cannot be cancelled. Trainers' next Pokémon come with Shift mode's offer to switch; a double faint sends out both sides.
+- PACK's Items pocket uses HP items (Potion, Berry and the rest of `HealingHPAmounts`) and status healers (Antidote, Parlyz Heal, Awakening, PSNCUREBERRY and the rest of `StatusHealingActions`) on any party Pokémon. Items with no battle use get Oak's warning. X items, Poké Doll, Full Restore and revives are refused.
 
 ## Native battles: current state
 
-The battle core, ROM tables, encounter hooks, battle UI and whiteout hooks are present. Unit tests cover wins, escape, loss, experience, move learning and capture; reference tests compare damage and type effectiveness. Browser tests drive a test-only wild encounter through the real UI: victory with level-up and move learning, escape, whiteout, catching with a nickname, keyboard and on-screen D-pad menu navigation, mid-battle backup restore, and rollback of unsupported effects. Real Route 29 encounters now use the ROM's encounter tables. Player switching and items other than balls in battle remain unfinished.
+The battle core, ROM tables, encounter hooks, battle UI and whiteout hooks are present. Unit tests cover wins, escape, loss, experience, move learning and capture; reference tests compare damage, type effectiveness, stat calculation and experience curves. Browser tests drive a test-only wild encounter through the real UI: victory with level-up and move learning, escape, whiteout, catching with a nickname, keyboard and on-screen D-pad menu navigation, mid-battle backup restore, rollback of unsupported effects, switching through the party menu and a Potion from the Items pocket. Real Route 29 encounters now use the ROM's encounter tables. Other battle items (X items, Poké Doll, Full Restore, revives) remain unfinished.
 
 This is still not a complete new game. Full party/bag/Pokégear menus, story progression beyond Route 30 and Mr. Pokémon's house, and audio remain unfinished. The Key Items menu supports the Bicycle; the PCs store Pokémon, items and decorations. Surfing and terrain animation now have native implementations; later maps remain gated. Save slots, a Johto/Kanto atlas, Pokédex records, online Link, friends and real-world steps come later.
 
@@ -209,24 +221,24 @@ their scripts and story progression are supported.
 
 - [x] Native player, party, Pokémon, bag, money and quest models with versioned saves
 - [x] Typed ROM decoders for species, moves, growth rates, items, encounters and trainers
-- [ ] Decoder for evolutions (not needed before the first evolution)
+- [x] Decoder for evolutions (the evolution itself is not ported yet)
 - [x] Mom, Elm's introduction, the starter, naming and the aide's Potion
 - [x] Route 29, Cherrygrove City, the Poké Mart and the Pokémon Center
 - [x] Route 30's trainers, Mr. Pokémon's house, the Mystery Egg and the Pokédex
 - [x] The Cherrygrove rival battle, Elm's call and the return to Elm
 - [x] Capture and the catching tutorial
 - [x] Battles: stats, damage, types, accuracy, criticals, status, turn order, fainting, experience, move learning, trainer AI, trainer send-outs and prize money
-- [ ] Player switching, and items other than balls, in battle
+- [x] Player switching, and HP and status healing items, in battle (X items, Poké Doll, Full Restore and revives are refused)
 - [x] The PC and boxes (catching with a full party)
 - [x] The introduction's naming and clock screens
-- [ ] Controlled-seed comparisons with the original beyond damage and type effectiveness
-- [ ] Acceptance: one continuous playthrough of the opening quest with save/reload. The scenes are tested individually from fixtures so far.
+- [ ] Controlled-seed comparisons with the original for random-driven routines (accuracy, criticals, damage variation, capture). Damage, types, stats and experience curves are compared.
+- [x] Acceptance: one continuous playthrough of the opening quest with save/reload (`tests/playthrough.test.ts`, driven through the world's inputs rather than the browser UI)
 
 Introduce native player, party, Pokémon, inventory, money and quest models. Read species, moves, growth curves, evolutions, encounters, trainers and items through typed ROM decoders. Define serialization/migrations before persisting new systems.
 
 Expand script calls, choices, scene state, inventory commands and native special handlers. Translate routines reached through assembly calls into explicit native services; never fall back to emulator execution in the shipping game.
 
-Meeting Mom, Elm's introduction, the starter, the aide's Potion, Route 29, Cherrygrove, Route 30's trainers, Mr. Pokémon's house, the Cherrygrove rival battle, the return to Elm, capture, the catching tutorial, the PC and the introduction's naming and clock screens run now. Next: player switching and other items in battle.
+Meeting Mom, Elm's introduction, the starter, the aide's Potion, Route 29, Cherrygrove, Route 30's trainers, Mr. Pokémon's house, the Cherrygrove rival battle, the return to Elm, capture, the catching tutorial, the PC, the introduction's naming and clock screens, and switching and healing items in battle run now. Next: controlled-seed comparisons of the random-driven battle routines.
 
 Complete and validate the native battle engine: deterministic randomness, stats, move selection, accuracy/critical checks, damage, status, turn order, switching, fainting, experience, capture and rewards. Compare controlled seeds and states with the original, including integer rounding and overflow behavior.
 
@@ -255,7 +267,7 @@ Acceptance: main-game/postgame playthroughs, representative optional content, ba
 - [x] Crystal-style shell with Game, Savegames, Map, Pokédex, Link and Friends tabs
 - [x] Adaptive canvas, live local minimap, keyboard and on-screen controls
 - [x] Save, backup export and import for the single native save
-- [x] Touch battle commands, move list, PACK (Balls pocket) and naming fields
+- [x] Touch battle commands, move list, PKMN party menu, PACK (Items and Balls pockets) and naming fields
 - [ ] Party, pack, PC and Pokégear menus outside battle
 - [ ] Scalable text, configurable controls and fuller accessibility
 - [ ] Save slots with migration, atomic writes and import previews