xsl:number implements all of XSLT 1.0 section 7.7: level
single/multiple/any with count and from matched as patterns through the
match cache, the value expression with the below-one bypass, and the
format-token engine (punctuation, separator and token reuse, zero
padding, alphabetic/roman/Greek sequences, digit grouping). An
unmatched single/multiple count renders empty; level=any always yields
a number. document() now caches per transform so repeated loads of the
same URI return the identical document and generate-id() stays unique
against live nodes (the idkey49 flake). Xalan baseline 557 -> 475
(numbering 84 -> 7).
