URLSearchParams crossing an implicit ToString (`${sp}`, "" + sp, String(sp))
had no lowering: ensureString now answers sp.toString, the serialized pair
list. Record inits also accept shorthand members (`new URLSearchParams({ model })`)
like the explicit `{ model: model }` spelling.
`re.exec(s)?.index` keeps the optional chain: the read is the match row's
index/input member (the chain lowering binds the guarded receiver first),
so the questionDotToken guard no longer diverts it.
Array.from(s) over a string whose binding the checker narrowed through a
guard read as the narrowed union and fenced; the site type now decides, and
the read is coerced to that string (code points, fresh array).
Corpus 8423-8425 pin all three against Node.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
