[PHP] fix: split host browser and SharedFS runtime fixes

[brandonpayton]

Summary

• split the host/browser/SharedFS runtime fixes out of mixed PHP PHPT PR Preserve shared mappings across fork for PHP PHPTs #717
• stack on [PHP] fix: split fork/process/shared-memory runtime fixes #737 via Automattic branch integration/kd-6nz-php-phpt-fork-process-shm-base
• keep this PR in the PHP harness stack, not targeted at main

Stack

• Harness PR: [PHP] Add upstream PHPT harness #736
• Prior stack: [PHP] fix: split socket datagram and multicast semantics #734 socket/network, then [PHP] fix: split fork/process/shared-memory runtime fixes #737 fork/process/shared-memory
• Direct base: integration/kd-6nz-php-phpt-fork-process-shm-base

Preserved commits

• 756f75c fix: unlink inline symlinks without following targets
• 99b5de8 fix: preserve dylink metadata during fork instrumentation
• 7a6aef7 fix: preserve instrumented wasm file permissions
• 17ef1dd fix: preserve omitted host utimens timestamps
• 78a5cb6 fix: align host-backed mount path resolution
• 39e770e fix: stabilize host-backed PHP test mounts
• 581ec3a fix: tighten browser DNS and PHPT output ordering
• 2c6474b fix: update sharedfs timestamps on content changes
• 13b0aad fix: honor socket peeking in browser network paths
• a2f3b3b fix: preserve browser child output and exec errors
• d50c868 fix: honor exclusive creates in sharedfs
• 23c6315 fix: keep virtual interface name APIs consistent
• 4f5b0c4 fix: keep memoryfs inode numbers representable
• a65f854 fix: speed up large SharedFS directories
• 0b1b8b5 fix: align SharedFS directory reads and append offsets
• 0e98540 fix: update SharedFS directory mutation times
• ce9aaa0 fix: tighten SharedFS rename semantics
• 45beda8 fix: reject trailing-slash unlink on files
• 439d699 fix: include service aliases in browser VFS
• 90281cf fix: arm browser VM interrupt timers from kernel worker
• aef48d5 Fix browser PHP PHPT runtime blockers
• 306a8e6 Preserve finite poll deadlines across retries
• 62a5771 Share main longjmp tag with side modules

Notes

• aa84b5b9f fix: stabilize parallel php harness server tests was not duplicated here because its effective OpenSSL config syscall work is already isolated in [PHP] fix: provide default openssl config file #726.

Verification

• git diff --check origin/integration/kd-6nz-php-phpt-fork-process-shm-base...HEAD

[brandonpayton]

Closing as superseded by origin-headed replacement #757: #757

This PR head was in brandonpayton/kandelo-agentic-dev. The replacement uses the same head SHA (62a5771) on an Automattic/kandelo origin branch and has an expanded description explaining why the change is needed and why it belongs in Kandelo.