fix: materialize local arrays and hashes before return

[fglock]

Summary

When returning localized arrays or hashes from subroutines, the values must be copied before local restoration occurs. Without this fix, returning local @ARGV would return ARRAY references to the restored (original) values instead of the localized values.

• Extended materializeSpecialVarsInResult() to copy RuntimeArray and RuntimeHash elements before local restoration happens
• Added regression tests for returning local arrays and hashes from subroutines

Problem

sub args {
    local @ARGV = @ARGV;
    @ARGV = ('modified');
    return @ARGV;
}
my @result = args();
# Before fix: @result was empty (restored original)
# After fix: @result is ('modified')

This was blocking Module::Build test suite where the args() method uses this pattern.

Test plan

• Unit tests pass (make test)
• New regression tests added in local.t
• Module::Build t/basic.t improved from 5 failures to 1 failure

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