textContent trimmed leading/trailing whitespace unconditionally before the
type's whiteSpace facet ran, so an xs:string (whiteSpace="preserve") value that
was whitespace-only or had significant edges was emptied or shortened: a tab
value did not match a \t pattern, a length facet undercounted, and so on.
Simple-content validation now reads the raw character content (rawTextContent)
and lets the facet normalize it (collapse types still trim/collapse through
process). The element-only and empty "no significant text" check keeps using
the trimmed form, so indentation whitespace between child elements is still
ignored.
XSTS: valid instances rejected 288 to 248. Baseline updated; regression tests
cover a preserved tab matching \t, a length facet counting whitespace, and
element-only content still ignoring indentation.
Refs #147, #129.
