feat: add Chinese soundtrack to Mahjong and Mahjong Match games

- Register 'chinese' music override for mahjong and mahjongmatch in soundtrack config
- Preload chinese-music.json in PreloadScene
- Lazy-load Chinese music assets via asset manifest for both games
- Update game scenes to use getGameSoundtrack() with volume support
- Update mahjong match background images (01, 02)

src/data/assetManifest.js

@@ -131,13 +131,21 @@ export const MANIFEST = {
     sheet('jello-items', 'assets/images/jello-items.png', 132, 132),
     image('bg-puddingmonsters-menu', 'assets/images/background-jello.png'),
   ],
-  mahjong: MAHJONG_TILES,
+  mahjong: [
+    ...MAHJONG_TILES,
+    // chinese soundtrack (see services/soundtrack.js) — lazy-loaded here so
+    // its audio only downloads once Mahjong is actually entered.
+    (scene) => musicFrom(scene, 'chinese-music'),
+  ],
   mahjongmatch: [
     ...MAHJONG_TILES,
     // Carries its own title, so the layout-select screen draws no heading.
     image('bg-mahjongmatch-menu', 'assets/images/background-mahjongmatch.png'),
     // In-play backdrops — one is picked at random per game.
     ...['01', '02', '03'].map((n) => image(`bg-mm-${n}`, `assets/images/background-mm-${n}.png`)),
+    // chinese soundtrack (see services/soundtrack.js) — lazy-loaded here so
+    // its audio only downloads once Mahjong Match is actually entered.
+    (scene) => musicFrom(scene, 'chinese-music'),
   ],
   spireclimb: [
     image('spireclimb-act1', 'assets/images/spireclimb-act1.png'),

src/games/mahjong/MahjongGame.js

@@ -6,6 +6,7 @@ import { api } from '../../services/api.js';
 import { createOpponentPortrait, createPlayerPortrait } from '../../ui/Portrait.js';
 import { playSound, SFX } from '../../ui/Sounds.js';
 import { MusicPlayer } from '../../ui/MusicPlayer.js';
+import { getGameSoundtrack } from '../../services/soundtrack.js';
 import {
   TILES, SUIT_NAMES, WIND_NAMES, rankOf, isSuited,
   FAAN_TABLE, MIN_FAAN, PLAYER_COLOR_HEX,
@@ -76,7 +77,10 @@ export default class MahjongGame extends Phaser.Scene {
   }
 
   create() {
-    try { new MusicPlayer(this, this.cache.json.get('music')?.tracks ?? []); } catch { /* optional */ }
+    try {
+      const { tracks, volume } = getGameSoundtrack(this);
+      if (tracks.length) new MusicPlayer(this, tracks, volume);
+    } catch { /* optional */ }
     this.add.rectangle(GAME_WIDTH / 2, GAME_HEIGHT / 2, GAME_WIDTH, GAME_HEIGHT, FELT).setDepth(DEPTH.bg);
 
     const names = [auth.user?.username ?? 'You'];

src/games/mahjongmatch/MahjongMatchGame.js

@@ -2,6 +2,7 @@ import * as Phaser from 'phaser';
 import { GAME_WIDTH, GAME_HEIGHT, COLORS } from '../../config.js';
 import { Button } from '../../ui/Button.js';
 import { MusicPlayer } from '../../ui/MusicPlayer.js';
+import { getGameSoundtrack } from '../../services/soundtrack.js';
 import { playSound, playSoundEx, SFX } from '../../ui/Sounds.js';
 import { api } from '../../services/api.js';
 import {
@@ -81,8 +82,8 @@ export default class MahjongMatchGame extends Phaser.Scene {
 
   create() {
     try {
-      const music = this.cache.json.get('music');
-      if (music?.tracks) new MusicPlayer(this, music.tracks);
+      const { tracks, volume } = getGameSoundtrack(this);
+      if (tracks.length) new MusicPlayer(this, tracks, volume);
     } catch (_) { /* optional */ }
 
     this.add.rectangle(GAME_WIDTH / 2, GAME_HEIGHT / 2, GAME_WIDTH, GAME_HEIGHT, FELT).setDepth(D.bg);

src/scenes/PreloadScene.js

@@ -47,6 +47,7 @@ export default class PreloadScene extends Phaser.Scene {
     this.load.json('arcadedark-music', 'data/arcadedark-music.json');
     this.load.json('hacker-music', 'data/hacker-music.json');
     this.load.json('adventure-music', 'data/adventure-music.json');
+    this.load.json('chinese-music', 'data/chinese-music.json');
     this.load.json('advancewars-artwork', 'data/advancewars-artwork.json');
     this.load.json('tetrisattack-artwork', 'data/tetrisattack-artwork.json');
     this.load.json('totalannihilation-artwork', 'data/totalannihilation-artwork.json');

src/services/soundtrack.js

@@ -29,7 +29,9 @@ export const GAME_SOUNDTRACK_OVERRIDES = {
   dotlink: 'hacker',
   '2048': 'hacker',
   swdbg: 'adventure',
-  spireclimb: 'adventure'
+  spireclimb: 'adventure',
+  mahjong: 'chinese',
+  mahjongmatch: 'chinese',
 };
 
 // Resolve the track list (and optional volume override) a game scene's