Fix filehandle I/O error semantics and handle-based chdir

[fglock]

CPAN compatibility failure

IO::Die 0.057 failed in CPAN run 20260828-172308-14550 (8 of 388 subtests).

The distribution is pure Perl. Focused upstream tests pass on system Perl 5.42, while both PerlOnJava backends reproduce the underlying failures.

Affected behavior

1. chdir($directory_handle) fails with The fchdir function is unimplemented. System Perl accepts directory handles for chdir.
2. Operations on invalid or closed filehandles do not follow Perl error semantics:
   • read(STDOUT, ...) succeeds even though STDOUT is not readable; IO::Die therefore cannot invoke a subclass's _CREATE_ERROR hook.
   • binmode($closed_handle) succeeds instead of failing with EBADF.
   • closedir($closed_handle) throws, but its error string has empty OS_ERROR and EXTENDED_OS_ERROR rather than Bad file descriptor.
   • chmod($filehandle) does not support the behavior exercised by IO::Die.

The original failures are in t/IO-Die.t: test_CREATE_ERROR, test_binmode, test_chdir, test_chmod, and test_closedir.

Reproducer

use IO::Die;

open my $fh, '<', '/dev/null' or die $!;
close $fh;
IO::Die->binmode($fh);

System Perl dies with a Binmode error containing :raw, layer, and Bad file descriptor. PerlOnJava returns success.

Likewise, this should succeed on a directory handle:

open my $dir, '<', '/' or die $!;
IO::Die->chdir($dir);

PerlOnJava reports fchdir as unimplemented.

Expected fix

Implement handle-based chdir, and make I/O operations consistently detect invalid descriptor state and preserve the correct OS error (EBADF) for wrapper code. Add focused project-owned regression coverage for JVM and interpreter backends.