Stdlib: date()/idate()/gmdate() format B — Swatch beats wrong (ext/date/php_date.c) #12224

Summary

date('B'), idate('B'), and gmdate('B') must return Swatch Internet Time beats (000–999) per php-src/timelib. This VM uses VmDate::swatchBeat() with a weekday-offset formula ($seconds + $daysFromMonday * 86400) instead of php-src’s ((timestamp + 3600) % 86400) / 86.4 (Biel/UTC+1 beats).

php-src reference: ext/date/php_date.c — B format branch; timelib swatch beat helper.

PHP implementation target: ext/standard/VmDate.php (swatchBeat(), idateValue(), date() B case) — port php-src formula; no new C runtime.

Repro (php-src-strict)

./script/docker-exec.sh -- bash -lc '
  php test/repro/maintainer_gap_idate_date_B_swatch.php
  php bin/vm.php test/repro/maintainer_gap_idate_date_B_swatch.php
'

Zend ($t = 1710000000): date('B') → '708'; idate('B') → 708; gmdate('B') → '708'
VM: all three → '5666' / 5666 (off by thousands)

Done when

• date('B'), idate('B'), gmdate('B') match php-src for fixed and current timestamps.
• Other idate() format chars unchanged.
• Compliance .phpt; php-src-strict.