PureXML.XPath.Budget is the configurable counterpart of libxml2's
fixed 10M node-set cap (libxml2Compatible preset included), thrown as
a located QueryError instead of a silent refusal, default unbounded.
xsl:sort honors lang with tailored alphabet orders for Polish and
Russian derived from the conformance golds, case-folded. The WASM
gate executes all 985 tests under wasmtime on an actual WASI runtime,
wired into CI; the first run caught a real wasm32 trap (Int is 32
bits there, so format-number's digit extraction trapped at 2^31
despite the 2^53 guard; internals are now Int64 and the xsl:number
bound is platform-correct). Xalan baseline 127 -> 125. Closes#143,
closes#144.