Long place names are truncated by a small text-max-width

• `Urumqi High-tech Industrial Development Zone` renders as two lines with the second line truncated
• `map.getLayer('district-label').layout['text-max-width']` is `4` with `text-size` 12
• No ellipsis and no ellipsis character appears, so the text looks clipped at the texture boundary

1. Read `layout['text-max-width']` and `text-size` for the layer
2. Estimate characters per line: max-width in em roughly equals Han characters per line
3. Temporarily set `text-max-width` to 20 and see whether the full name appears
4. Check for a custom clip post-process or `overflow: hidden` on the container
5. Measure the label texture height against the allowed number of lines

Raise `text-max-width` to 8 to 12 for Chinese, interpolate `text-size` by zoom (`['interpolate', ['linear'], ['zoom'], 8, 11, 14, 13, 17, 15]`), set `text-line-height: 1.2`, and insert a line break at a semantic boundary for names longer than about 8 characters.

console.log(map.getLayer('district-label').layout['text-max-width']);   // 4
console.log(map.getLayer('district-label').layout['text-size']);        // 12
// 若同时 text-max-width 4 + text-size 12，字号 12px，可行宽度约 48px

map.addLayer({
  id: 'district-label',
  type: 'symbol',
  source: 'districts',
  layout: {
    'text-field': ['get', 'name'],
    'text-size': ['interpolate', ['linear'], ['zoom'], 8, 11, 14, 13, 17, 15],
    'text-max-width': 10,          // 中文每行约 10 字
    'text-line-height': 1.2,
    'text-max-angle': 30,
    'symbol-placement': 'point'
  },
  paint: {
    'text-color': '#1b2733',
    'text-halo-color': '#ffffff',
    'text-halo-width': 1.2
  }
});

• Treating `text-max-width` as pixels or as a character count and setting it to 4 for short labels
• Fixing the width but leaving `text-size` fixed, so a long name at high zoom still exceeds the texture height