[EPIC] PHP 8.6 support — full reflection parity

[lisachenko]

Goal

Bring goaop/parser-reflection to full parity with PHP 8.6 (GA planned for 2026-11-19, currently in beta). This epic tracks all PHP 8.6 features that affect static reflection, following the same approach used for the 8.4/8.5 cycles (#162, #209).

Context

• Master targets PHP 8.5+; CI already runs an experimental (allowed-to-fail) PHP 8.6 job in .github/workflows/phpunit.yml.
• ReflectionEngine parses with PHP-Parser's newest supported grammar by default, so new 8.6 syntax support arrives via nikic/php-parser upgrades (currently ^5.4, latest is 5.8.0 which does not yet parse the 8.6 partial-application ? placeholder).
• Runtime-parity tests against native reflection must be guarded with PHP_VERSION_ID >= 80600 where they exercise 8.6-only behavior, mirroring the existing per-feature stub pattern (tests/Stub/FileWith*85.php → FileWith*86.php).

PHP 8.6 features in scope (accepted/implemented RFCs)

Feature	Reflection impact	Sub-issue
Function parameter doc comments	ReflectionParameter::getDocComment() must be emulated from AST	TBD
ReflectionProperty::isReadable() / isWriteable()	New methods to emulate statically (visibility, asymmetric visibility, readonly, hooks)	TBD
Readonly property defaults	getDefaultProperties() / ReflectionProperty::getDefaultValue() semantics change	TBD
Partial Function Application (? / ... placeholders)	Parsing must not break; blocked on upstream PHP-Parser support	TBD
#[\Override] on class constants + __debugInfo() on enums + attribute API additions (ReflectionAttribute::getCurrent() — verify final status)	Stub coverage + parity tests	TBD
Internal functions gaining #[\Deprecated] (e.g. strcoll())	isDeprecated() parity for internal functions	#215
8.6 deprecations (is_double()/is_integer()/is_long(), return from finally, etc.) + test scaffolding	Library must run deprecation-clean on 8.6; shared 8.6 stub/guard infrastructure	TBD

Out of scope (no reflection surface): clamp(), SortDirection enum, Time\Duration, polling API, pack/unpack endianness modifiers, session/security defaults, closure performance optimizations.

Delivery process

• Each sub-issue is implemented on its own branch in an isolated worktree by a dedicated agent (max 4 in parallel) and lands as a separate PR referencing its sub-issue.
• PRs are reviewed by the orchestrating session; final accept/merge stays with @lisachenko.
• Definition of done per sub-issue: implementation + stubs + parity tests green on PHP 8.5 (and on the 8.6 experimental job where the runtime allows), PHPStan level 10 clean.