THRIFT-5976: Add native types to PHP library properties (PHPDoc @var → declared types)

[sveneld]

Summary

Convert PHPDoc @var T annotations on properties throughout lib/php/lib/ to native PHP typed properties. PHP 8.1+ enforces these at runtime and phpstan can verify access. This is a no-LSP-cascade additive change — typed properties don't impose covariance constraints on subclasses beyond requiring redeclarations to use the same type.

JIRA: https://issues.apache.org/jira/browse/THRIFT-5976 (sub-task of THRIFT-5960).

Scope

• 33 files in lib/php/lib/ (Base, ClassLoader, Exception, Factory, Protocol incl. JSON / SimpleJSON contexts, Server, Transport, StoredMessageProtocol, TMultiplexedProcessor) — properties typed bool / int / string / float / array / object plus class types (TTransport, TServerTransport, TProtocol, TTransportFactoryInterface, TProtocolFactory, …).
• Resource handles (TPhpStream::$inStream/$outStream, TSocket::$handle, THttpClient::$handle, TServerSocket::$listener, TSSLSocket::$context) kept untyped with @var resource|null PHPDoc since PHP has no native resource type.
• Static arrays (TBase::$tmethod, TException::$tmethod, TApplicationException::$tspec, TCompactProtocol::$ctypes/$ttypes) declared static array with shape annotations.
• Constructor property promotion in JSON / SimpleJSON contexts and TBinaryProtocolFactory where the ctor body was simply argument→property assignment.
• Dropped nullable-fiction on PairContext::$protocol — methods always dispatch through it, so null was never a valid state.
• SimpleJSON\MapContext — remove the shadowing private $protocol (parent StructContext owns it; MapContext never reads it directly), type the constructor argument as TSimpleJSONProtocol and forward to parent.
• TJSONProtocol::$context / $reader typed against BaseContext / LookaheadReader (short names; uses already present).

Notable fixes surfaced by typing

• TSocket::$port = '9090' (string default while PHPDoc said int) → 9090.
• TSocketPool::__construct now passes '' instead of null to parent TSocket::__construct since TSocket::$host became typed string. $this->host is reassigned per-server in TSocketPool::open(), so the empty default is never observed externally.
• TCurlClient::$response typed string|false|null to reflect both the null-initialised state and curl_exec's string|false return.
• TMultiplexedProcessor::$serviceProcessorMap was implicitly null and promoted to a map on first registerProcessor call; explicitly initialised to [].

Test fixtures

• JsonProtocolStub now extends TJSONProtocol (concrete class, no abstract methods to satisfy) so the context properties can be typed concretely. Keeps only the readJSONSyntaxChar override that records call arguments.
• SimpleJsonProtocolStub removed — after being rewritten as extends TSimpleJSONProtocol with no overrides it was equivalent to the real class. Tests now instantiate TSimpleJSONProtocol directly.

Out of scope (separate sub-tickets under THRIFT-5960)

• Method parameter / return types.
• declare(strict_types=1) rollout.
• PHP code generator (t_php_generator.cc) changes.
• phpstan ratchet level 1 → 5.

Verification (in PHP 8.4 / composer 2 / phpstan 1.12 / phpunit 13 docker)

composer phpstan         OK (level 1, baseline unchanged)
vendor/bin/phpcs         OK
phpunit Unit suite       629 tests, 1907 assertions, 0 errors
phpunit Integration      106 tests,  166 assertions, 0 errors

Checklist

• Did you create an Apache Jira ticket? — THRIFT-5976
• If a ticket exists: Does your pull request title follow the pattern "THRIFT-NNNN: describe my issue"?
• Did you squash your changes to a single commit?
• Did you do your best to avoid breaking changes? — yes; native typed properties tighten what was already documented in PHPDoc. Edge cases (timeout int|float|null, resource-typed handles, mock-friendly contexts) preserved.
• If your change does not involve any code, include [skip ci] anywhere in the commit message to free up build resources.