Play the music and sound effects from the ROM's sound engine (Closes #34)

The sound engine (audio/engine.asm, home/audio.asm) is ported on a byte
copy of its audio WRAM and a sound register model. A reference test runs
the cartridge's routines beside it and matches the WRAM and registers
after every UpdateSound for all songs, effects and cries, fades, the
danger tone and effect priority. apu.ts synthesizes the four channels in
an AudioWorklet; its output matches the reference emulator's APU by
spectrum. The world runs the engine twice per tick; Play or the first
press unlocks sound, pausing suspends it, Settings sets the volume.

Wired in: map music by map setup and special map music, script audio
commands, text fanfares, WaitSFX and cries that hold the script frozen
(the last page stays shown), battle music, cries, fainting, victory,
capture and the low HP tone, Pokémon Center healing, evolution, the
intro, the Pokédex's cries, PCs, marts, healing items, talk and menu
clicks, bumps, ledges, warps, boulders, the Bicycle and Surf.

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

README.md

@@ -12,7 +12,7 @@ North of Cherrygrove, Route 30's trainers battle you. Bug Catcher Don spots you
 
 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 or opens a Pokémon's stats, and when one faints you choose the next. PACK's Items pocket uses healing items, revives, Ethers, X items and Poké Dolls.
 
-Start opens the start menu. POKéMON shows your party: open a Pokémon's stats, change the order, rearrange its moves, or give and take held items. PACK shows your pockets: use Potions, status healers, revives, Ethers, PP Ups, vitamins, Rare Candy and evolution stones, give or toss items, and ride the Bicycle. Pokémon evolve when they level up after a won battle (press B during the flashes to stop it), and learn new moves outside battle too. Field moves work from the party menu too: Cut, Surf, Strength, Flash, Whirlpool, Waterfall, Sweet Scent, and Softboiled or Milk Drink to share HP. Fly opens the Fly map to choose a town you have visited, Teleport returns to the town of the last Pokémon Center you entered, and Dig or an Escape Rope leads out of a cave through the entrance you last used. In PACK, SEL registers a key item such as the Bicycle, and Select then uses it. POKéGEAR shows the clock, the Town Map card with a cursor over every landmark, and the phone: call Mom or Professor Elm. Call Mom after the catching lesson and she offers to save some of your trainer prize money. Once the Mystery Egg is delivered, talk to her at home to save or take money, or to switch Daylight Saving Time; with enough saved, she buys items and dolls for you and calls to say so. POKéDEX lists Pokémon in Johto order up to the last one you have seen. Open a seen Pokémon to read its number, category and footprint; once caught, its height, weight and two pages of text appear. Your name in the start menu opens the trainer card: your ID, money, Pokédex count and play time, then the Johto leaders with the badges you have earned. OPTION sets the battle style (SET skips the offer to switch when a trainer sends out the next Pokémon) and the menu account (the start menu's descriptions); text speed, battle scene, sound, print and frame are kept for later. Bill's PC can move Pokémon between the party and any box. The poster opens the Town Map.
+Start opens the start menu. POKéMON shows your party: open a Pokémon's stats, change the order, rearrange its moves, or give and take held items. PACK shows your pockets: use Potions, status healers, revives, Ethers, PP Ups, vitamins, Rare Candy and evolution stones, give or toss items, and ride the Bicycle. Pokémon evolve when they level up after a won battle (press B during the flashes to stop it), and learn new moves outside battle too. Field moves work from the party menu too: Cut, Surf, Strength, Flash, Whirlpool, Waterfall, Sweet Scent, and Softboiled or Milk Drink to share HP. Fly opens the Fly map to choose a town you have visited, Teleport returns to the town of the last Pokémon Center you entered, and Dig or an Escape Rope leads out of a cave through the entrance you last used. In PACK, SEL registers a key item such as the Bicycle, and Select then uses it. POKéGEAR shows the clock, the Town Map card with a cursor over every landmark, and the phone: call Mom or Professor Elm. Call Mom after the catching lesson and she offers to save some of your trainer prize money. Once the Mystery Egg is delivered, talk to her at home to save or take money, or to switch Daylight Saving Time; with enough saved, she buys items and dolls for you and calls to say so. POKéDEX lists Pokémon in Johto order up to the last one you have seen. Open a seen Pokémon to read its number, category and footprint and hear its cry (CRY plays it again); once caught, its height, weight and two pages of text appear. Your name in the start menu opens the trainer card: your ID, money, Pokédex count and play time, then the Johto leaders with the badges you have earned. OPTION sets the battle style (SET skips the offer to switch when a trainer sends out the next Pokémon), the sound (mono or stereo) and the menu account (the start menu's descriptions); text speed, battle scene, print and frame are kept for later. Bill's PC can move Pokémon between the party and any box. 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.
 
@@ -32,7 +32,9 @@ Routes 45 and 46 lead south from Blackthorn back to Route 29. In Ecruteak, the C
 
 On Route 40, the Battle Tower takes a party of three different Pokémon holding different items into a Battle Room of the level you choose, against seven trainers in a row. Win them all for five of a random vitamin. Between battles you can save and quit, and the receptionist picks up where you left off.
 
-Kanto, the League, Olivine's port and the S.S. Aqua, the Day-Care's Eggs, trade evolutions, the Pokégear's radio, the Pokédex's area view, search and other list modes, and audio are still being ported. Unported neighboring areas appear at the edges but cannot be entered yet.
+The music and sound effects play from your ROM's own sound engine: map music, battles and their cries, fanfares, jingles and fades. Sound starts with your first press (browsers require it) and pauses with the game; Settings turns it down or off. Move animations and their sounds are not ported.
+
+Kanto, the League, Olivine's port and the S.S. Aqua, the Day-Care's Eggs, trade evolutions, the Pokégear's radio, the Pokédex's area view, search and other list modes are still being ported. Unported neighboring areas appear at the edges but cannot be entered yet.
 
 ## Run
 
@@ -45,7 +47,7 @@ npm run dev
 
 Open the printed local URL and select your uncompressed **English US/Europe revision 1.1** ROM (`.gbc`, 2 MiB). Its checksum is verified locally. ROMs are never uploaded or stored in browser storage; select yours again after reloading to resume. A new game starts with Professor Oak's introduction, where you choose your character, set the clock and pick a name.
 
-Use onscreen controls, or focus the game screen and use arrows to move, **X** to interact and **X / Z** to continue dialogue. **Settings** changes these keys and the text size for this browser. In choices, **Up / Down** change the answer, **X** confirms and **Z** answers No. Sessions save every 10 seconds and when paused. Switching apps pauses play. Download a backup before clearing browser data.
+Use onscreen controls, or focus the game screen and use arrows to move, **X** to interact and **X / Z** to continue dialogue. **Settings** changes these keys, the text size and the sound volume for this browser. In choices, **Up / Down** change the answer, **X** confirms and **Z** answers No. Sessions save every 10 seconds and when paused. Switching apps pauses play. Download a backup before clearing browser data.
 
 Native saves are separate from emulator snapshots and cartridge `.sav` files. Saving during a scene keeps the progress from before it, so the scene replays after loading. The time you give Oak is kept as an offset from the device clock (the steppers start at the device's time), and the weekday you give Mom as an offset from that clock's weekday. The tile counter measures in-game movement, not real-world steps.