String input copies its UTF-8 once into owned storage (an unsafe
pointer encapsulated in a class lifetime, never escaping the parser)
and scalars decode straight off the pointer, eliminating the
per-character closure chain; ASCII literals match and consume at the
byte level; and plain-ASCII character data scans as a single byte run
with one String built per run. Parse drops 32 percent cumulative
(0.49 s to 0.34 s on the 4.2 MB corpus, libxml2 ratio 30x to 20x).
The W3C suite caught one boundary (a run starting with '>' could
swallow the ]]> check after the character path consumed ]]); the run
scanner leaves a leading '>' to the character path, pinned as a unit
regression. All conformance suites, Linux, and WASM verified.
