Brings in the review merge and "Keep an Error's code slot in step with
dynamic writes and own properties". With main's split, `'code' in err`
(now the runtime's error.hasCode) lands in expressions/relational.ts.
Corpus 6417-error-code-dynamic-writes renumbers to 6415 (main has its own
6417), and the corpus-cost entries of 6407/6408 follow their renumbering
to 6412/6413.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Chris Tate