A missing sprite key silently drops the whole symbol

• No icon and no label is drawn for the layer even though the source has features
• `'poi-restaurant' in sprite` is `false` after fetching `/sprite.json`
• The sprite keys are `['restaurant', 'hospital', 'parking']`

1. Fetch `sprite.json` and search for the exact `icon-image` value
2. Print `layout['icon-image']` to see whether it is a literal or a `['get', ...]` expression
3. Check the distinct property values in the data for case, hyphen and underscore differences
4. Confirm the style's `sprite` URL points at the same sprite version
5. Diff every icon value in the data against the sprite keys

Align names with the sprite keys generated by `spritezero sprite ./icons` (the key is the file name without extension), and validate on load with a whitelist: `f.properties.icon = ICONS.has(raw) ? raw : 'marker-default'`.

const sprite = await fetch('/sprite.json').then(r => r.json());
console.log(Object.keys(sprite));   // ['restaurant', 'hospital', 'parking', ...]

console.log(map.getLayer('poi').layout['icon-image']);   // 'poi-restaurant'
console.log('poi-restaurant' in sprite);                   // false

spritezero sprite ./icons
# 生成 sprite.json / sprite.png，键名取自文件名（不含扩展名）
# icons/restaurant.svg  ->  键 'restaurant'

• Waiting for a console error to catch a bad icon name, since Mapbox GL fails silently on missing sprite keys
• Renaming sprite keys but leaving `icon-image` values with the old prefix, so every POI disappears