`...(x ?? {})` and `...(x || {})` spread exactly what `...x` spreads, but
the defaulted source lowered as a `??` expression into a checked-dynamic
value, which failed for records with function fields. When x is a record
or an optional record, the spread now lowers as a spread of x.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
