DOM: insertBefore($n,$n) throws Error previous sibling (#22686)

[PurHur]

Summary

• Guard DOMNode::insertBefore($n, $n) in VmDom so same-node insert raises Error: Cannot add newnode as the previous sibling of refnode before detach (php-src ext/dom/node.c), instead of DOMException: Not found error.
• Wire user-script AOT insertBefore via JitDomInsertBefore + DomCreateElementJitHelper (same pattern as replaceChild).
• Compliance + repro + AOT reorder smoke; spine/inventory synced.

Closes #22686

php-src reference

• ext/dom/node.c — dom_node_insert_before / libxml xmlAddPrevSibling failure when new == ref

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/vm.php test/repro/issue_22686_dom_insertbefore_self_ref.php'
# Error:Cannot add newnode as the previous sibling of refnode / PASS

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php bin/jit.php test/repro/issue_22686_dom_insertbefore_self_ref.php'
# PASS

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && vendor/bin/phpunit --filter dom_node_insertbefore_self_ref'
# OK (2 tests)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && export PHP_COMPILER_HELPER_RUNTIME_O=1 && php vendor/bin/phpunit test/aot/AotTest.php --filter dom_node_insertbefore_reorder'
# OK (1 test)

php script/bootstrap-inventory.php --check   # OK 6505/6505
php script/check-selfhost-spine-coverage-sync.php  # OK

Test plan

• VM repro Regression: DOMNode::insertBefore($n, $n) throws Not found — Zend Error previous sibling (ext/dom/node.c) #22686
• JIT repro
• Compliance dom_node_insertbefore_self_ref.phpt
• AOT reorder smoke (insertBefore bridge)
• Inventory + spine coverage

Made with Cursor

[PurHur]

Cleanup bot: deleted leftover remote branch agent/issue-22686-insertbefore-self-ref (squash-merged here; issue #22686 closed; tip already on master).