Collect is the all-errors-at-once counterpart to All. All still stops at
the first failure (unchanged); Collect runs every function and returns the
failures joined with errors.Join, which errors.Is still matches element by
element. Kept as a separate function rather than a flag on All so All's
signature and behaviour don't change.
Closes#5
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
