Remove dead code in Profiler, add static analysis annotations

[simon-mundy]

Summary

Minimal src/-only changes that remove provably dead code and add static analysis annotations. No behavioural changes.

Changes

src/Adapter/Profiler/Profiler.php — Remove unreachable else-branch in profilerStart()

The method signature is string|StatementContainerInterface $target. The if handles StatementContainerInterface, the elseif handles string. PHP's union type enforcement means no other type can reach the method body — the else branch with its InvalidArgumentException throw is dead code. Removed the branch and cleaned up the now-unused InvalidArgumentException import and is_string() import.

src/Adapter/Driver/Pdo/AbstractPdo.php — Add @codeCoverageIgnore to checkEnvironment() throw

The throw fires when extension_loaded('PDO') returns false. But AbstractPdo itself requires the PDO extension to be loaded (it imports PDO classes). Any environment where this class is instantiable necessarily has PDO loaded, making the throw unreachable in practice.

src/ResultSet/AbstractResultSet.php — Add @phpstan-ignore for Traversable assignment

In initialize(), after the array and IteratorAggregate branches are handled, the remaining $dataSource is a Traversable that is necessarily an Iterator. PHPStan cannot narrow Traversable to Iterator here, so the ignore annotation is appropriate.

Test plan

• ./vendor/bin/phpunit — all 1446 tests pass
• ./vendor/bin/phpstan — 0 errors
• ./vendor/bin/phpcs — no new violations
• Verify no behavioural changes — only dead code removal and annotations