fix(scripts): repoint remaining rewind --list callers to checkpoint list --pending --json

The rewind --list surface was removed in favor of checkpoint list --pending --json, and the SKILL.md prose reference was migrated, but two executable callers were missed: the test-repo harness list-rewind-points action and the attribution e2e script (steps 9 and 15). They invoked the removed --list flag, which now fails with "unknown flag".

Repoint both to the drop-in replacement (identical JSON output) so the dev harnesses keep working.