fix(reflection): skip closures over internal functions when walking the live closures

[lisachenko]

What this changes

A body swap walks the live closure objects to find the copies of its entry (fake closures share the entry's run-time cache and borrow its live statics; see FunctionBodySwap::liveClosureFunctions()). The walk built a user-function view over every closure and only then asked whether it was user-defined. A closure over an internal function (a first-class callable strlen(...), Closure::fromCallable('strlen'), the closure of an internal method) keeps its name in the internal_function member, so building the view threw FFI\Exception: Attempt to read undefined field 'function_name' first. Every redefine() that released a minted run-time cache, let a preserveAs alias take over live statics, or retired a removed alias failed while such a closure was alive anywhere in the process.

Found through the cascade of 8.5 into master (#285/#289): PHP 8.6 keeps closures over internal functions in its callable caches, so there every one of those paths failed (14 errors). Reproduced on PHP 8.4 with a strlen(...) kept alive across two swaps. It exists on every branch since the feature landed, so the fix targets 8.4 and cascades.

The function type is now read off the zend_function union before any view is made, with the same ZEND_USER_FUNCTION test FunctionLikeTrait::isUserDefined() uses, and internal closures are skipped. RedefineLiveInternalClosureTest holds the three kinds of internal closure alive through the cache release, the alias take-over of live statics and removeMethods(), in both runner modes.

The same hunk is ported into #289 so the 8.6 cascade can go green without waiting for this one; it no-ops once the cascade carries it.

Environment it was verified on

• PHP version (full first line of php -v): PHP 8.4.19 (cli) (built: Oct 10 2026) (NTS)
• Thread safety: NTS
• OS / architecture: Linux x86_64
• Debug build (--enable-debug)? no

Verified: the new test in both runner modes, composer test (minus the pre-existing ExecutionDataTest::testGetThis abort of this build), composer phpstan, composer cs:check.

Checklist

• Targets the minimum affected version branch (master = newest
  supported minor, 8.4 = PHP 8.4, …) — fixes cascade upward, never
  downward
• composer test passes on the matching PHP minor
• composer phpstan (level max) and composer cs:check are green
• Tests added or updated; structs the code dereferences are listed in
  layout_structs in tools/generator/symbols.php (nothing new)
• If tools/generator/symbols.php changed: regenerated with
  composer gen-headers and committed the result — nothing under
  include/, stubs/ or .phpstorm.meta.php was hand-edited (unchanged)
• Conventional Commits used for the commit messages

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