[BUG] Description of built-in arguments is lost when used in custom map args

[zstadler]

Describe the bug
When overriding any of the builtin args in a custom map yaml definition, the description is lost

To Reproduce
Steps to reproduce the behavior:

1. Download railways.yaml
2. Add minzoom: 10 to args
3. Run command docker run --rm -v .:/w -w /w ghcr.io/onthegomap/planetiler railways.yml --help | grep "(no .*)"
4. See 0:00:00 DEB - argument: minzoom=10 (no description provided)

Expected behavior
See 0:00:00 DEB - argument: minzoom=10 (minimum zoom level)

Environment

• Hardware: WSL Docker
• OS: WSL Docker
• Planetiler build version: 0.8.4-SNAPSHOT
• Planetiler build timestamp: 2024-12-07T10:56:55.013Z

Additional context
My usual workaround was to copy the description into args. For example:

args:
  max_point_buffer:
    description: "Additional global limit for the max tile pixels to include points outside tile bounds of all layers.  Set to a lower value to reduce tile size for clients that handle label collisions across tiles (most web and native clients). NOTE: Do not reduce if you need to support raster tile rendering"
    default: 0

However, this is not possible for minzoom and maxzoom.

args:
  minzoom:
    default: 10
    description: minimum zoom level

produces a "Cannot override built-in argument: minzoom" exception:

0:00:00 DEB - argument: schema=railways.yml (Location of YML-format schema definition file)
Exception in thread "main" com.onthegomap.planetiler.custommap.expression.ParseException: Cannot override built-in argument: minzoom
        at com.onthegomap.planetiler.custommap.Contexts.lambda$buildRootContext$0(Contexts.java:87)
        at java.base/java.util.Map.forEach(Map.java:733)
        at com.onthegomap.planetiler.custommap.Contexts.buildRootContext(Contexts.java:80)
        at com.onthegomap.planetiler.custommap.ConfiguredMapMain.main(ConfiguredMapMain.java:48)
        at com.onthegomap.planetiler.Main.main(Main.java:102)