Stdlib: AOT filesize/filemtime via libc stat fields (#27013)

[PurHur]

Summary

• Fixes AOT filesize() / filemtime() / sibling long fields returning garbage (type-tag 1 or pointer-sized ints) while VM/JIT matched Zend.
• Root cause: thin AOT NestedJIT of StatFieldsJitHelper::longField → VmStatCache arrays mis-reads values; path predicates already used libc via JitStatKernel.
• Long-field ABI bridge now reads glibc struct stat offsets through JitStatKernel::longField (peer #19215 mode kernel / FtokRuntime).

Closes #27013

php-src reference

• ext/standard/filestat.c — PHP_FUNCTION(filesize) / php_stat
• Implementation: ext/standard/JitStatKernel.php, ext/standard/JitStatPathKernel.php

Test plan

• Issue repro (VM/JIT/AOT):

  ./script/docker-exec.sh -- bash -lc '
  php bin/vm.php test/repro/issue_27013_aot_filesize.php
  php bin/jit.php test/repro/issue_27013_aot_filesize.php 2>/dev/null | grep -v Deprecated
  php bin/compile.php -o /tmp/aot_27013 test/repro/issue_27013_aot_filesize.php && /tmp/aot_27013
  '

  → all print 2
• AOT repeat: 10/10 runs print 2
• Sibling fields on /etc/hostname match Zend under AOT
• vendor/bin/phpunit --filter 'FilesizeBuiltinTest|StatPathRuntimeShrinkTest' → OK
• Not covered: full ci-local / compliance sweep; unrelated helper-runtime KeySort/ValueSort prelink staleness

Gate snapshot (before claim)

• docker info: OK
• release-readiness: blocked by unrelated stale KeySort/ValueSort helper prelink; gen0-driver-functional ok

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