php-in-php: runtime shrink closeout guard (#5211)

[PurHur]

Summary

• Adds RuntimeShrinkCloseoutTest — single inventory guard that the php-in-php queue’s deleted lib/AOT/runtime/*.c files stay gone and PHP SSOT paths remain linked.
• Adds test/repro/issue_enum_unserialize_roundtrip.php (repro cited by Stdlib: unserialize() must restore backed enum case singleton from Zend serialize payload (var_unserializer.c) #5739; green on master).

C runtime surface today: only lib/AOT/runtime/phpc_progress.c (~31 lines, frozen SIGSEGV ABI per #7360). All other migrated TUs are LLVM/PHP in ext/ + lib/JIT/Builtin/.

Closes #5200
Closes #5258
Closes #5278
Closes #5280
Closes #5290
Closes #5363
Closes #5302
Closes #5227
Closes #5234
Closes #5708

Verification

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php vendor/bin/phpunit --filter RuntimeShrinkCloseoutTest'
# OK (3 tests, 60 assertions)

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php vendor/bin/phpunit --filter AotRuntimeInventoryTest'
# OK — only phpc_progress.c under lib/AOT/runtime/

./script/docker-exec.sh -- bash -lc 'source script/php-env.sh && php test/repro/issue_enum_unserialize_roundtrip.php'
# E:3:"E:A";
# \E::A
# same

Lines removed (prior merges, inventory)

Deleted C TU	~lines	PHP SSOT
phpc_settype.c	~400	ext/standard/JitSettype.php
phpc_dir.c	~171	lib/JIT/Builtin/StringDirJit.php
phpc_fs_dir.c	~525	lib/JIT/Builtin/StringFsDirJit.php
phpc_unserialize.c	~344	lib/JIT/Builtin/StringUnserializeJit.php + VmSerialize.php
phpc_string_cslashes.c	~349	ext/standard/VmString.php
phpc_class_methods.c	~201	ext/standard/get_class_methods_.php
phpc_ini_set.c	~230	lib/JIT/Builtin/IniRuntime.php
phpc_json_decode.c	~649	lib/JIT/Builtin/StringJsonDecodeJit.php
hash_crypto.c	varies	lib/JIT/Builtin/StringHashCryptoNativeJit.php
password_crypto.c	~362	lib/JIT/Builtin/StringPasswordCryptoJit.php

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