Stdlib: fputcsv() CSV option ValueError parity (#4530)

[PurHur]

Summary

• Add VmCsvArg / JitCsvArg PHP validation for fputcsv() separator, enclosure, and escape arguments matching php-src ext/standard/file.c (PHP_FUNCTION(fputcsv) / php_csv_handle_escape_argument).
• VM path validates before VmFs::fputcsv() instead of relying on host \fputcsv() delegation.
• JIT/AOT path emits compile-time and runtime ValueError for invalid option strings.

php-src reference

• php/php-src ext/standard/file.c — _php_fputcsv, php_csv_handle_escape_argument

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter fputcsv'
# OK (11 tests, 13 assertions)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php test/repro-maintainer/fputcsv_escape.php'
# enclosure empty / escape two → ValueError matching Zend

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/compile.php -l test/fixtures/aot/compile-only/fputcsv_escape.php'
# lint_exit=0

Closes #4530

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