Style fails to load and the map stays a grey background

• Error: Could not load style: https://styles.example.cn/basic/style.json at Style.load (style.ts:673).
• Uncaught Error: style is not done loading on every addLayer call.
• map.isStyleLoaded() stays false while the background shows the #f2f4f6 default fill.

1. Register map.on('error') to surface errors MapLibre otherwise swallows.
2. Fetch the style URL and print status, content-type and the parsed sprite and glyphs fields.
3. Check the network panel for 404, a CORS block or net::ERR_CERT_AUTHORITY_INVALID.
4. Validate that the JSON parses, not just that it returns 200.

Serve style.json same-origin with absolute sprite and glyphs paths, keep a minimal inline background-only fallback style, then map.setStyle() after the fetch resolves, and add sources and layers inside map.on('load').

Error: Could not load style: https://styles.example.cn/basic/style.json
    at Style.load (style.ts:673)
Uncaught Error: style is not done loading

map.on('error', function (e) {
  console.error('地图错误', e.error && e.error.message, e.sourceId, e.tile);
});

• Calling addLayer right after the Map constructor throws and leaves an empty style that never recovers without setStyle.
• Writing sprite and glyphs as relative paths makes them resolve against the style.json directory and 404.