Which issue, if any, is this issue related to?

Closes #6891

Is there anything in the PR that needs further explanation?

I forgot about <urange> productions when migrating rules to @csstools/css-tokenizer.

Parsing <urange> requires special handling and should only be done when inside a context that expects such values.

I've added a helper (isUnicodeRangeDescriptor) to make it easier for rules to skip @font-face { unicode-range: U+0100-024F; }