Bug report

Sealing a non-abstract class removes some benefits of the sealing (we cannot do exhaustive checks on child classes to cover all cases), but it is still a valid use case: allowing inheritance only for my own classes and not for third-party classes.
However, phpstan does not handle this properly. When migrating the scssphp/scssphp codebase from the jiripudil/phpstan-sealed-classes extension to the @phpstan-sealed annotation, some errors were reported for such usage: https://github.com/scssphp/scssphp/actions/runs/18893747531/job/53926840383?pr=815#step:5:10

Code snippet that reproduces the problem

https://phpstan.org/r/51419802-fa2a-459d-8079-744ec3452857

Expected output

Type assertions should pass.
This snippet is a port of https://github.com/jiripudil/phpstan-sealed-classes/blob/main/tests/data/allowed-subtypes-non-abstract-class.php from the testsuite of jiripudil/phpstan-sealed-classes, with the only change being migrating from their Sealed attribute to the @phpstan-sealed annotation.

See https://github.com/jiripudil/phpstan-sealed-classes/blob/2a577dac4afae03dd9271b7e2978cc5aa50c0df9/src/SealedClassAllowedSubTypesClassReflectionExtension.php#L49-L51 for the logic handling it in jiripudil/phpstan-sealed-classes

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