concurrent-ruby rspec testsuite fails with ruby4.0.0dev perhaps due to Set change

Trying with ruby 4.0.0dev (2025-11-16 master bacd35626c) +PRISM [x86_64-linux]
https://github.com/ruby/ruby/commit/bacd35626c500db1f27136b57363685e4da74d9b

concurrent-ruby git head
https://github.com/ruby-concurrency/concurrent-ruby/commit/05523c01f6f2eebcb7579c2b8efc29e595010bb0
concurrent-ruby side rspec testsuite fails (concurrent-ruby-edge side not tested) like:

$ env RUBYLIB=$(pwd)/lib/concurrent-ruby rspec --exclude-pattern 'spec/concurrent/{actor_spec.rb,channel_spec.rb,lazy_register_spec.rb,channel/**/*,edge/**/*,processing_actor_spec.rb,promises_spec.rb,throttle_spec.rb,cancellation_spec.rb,executor/wrapping_executor_spec.rb}'

......
Failures:

  1) Concurrent::Set.[] when initializing with arguments creates a set with the given objects
     Failure/Error: monitor or raise("BUG: Internal monitor was not properly initialized. Please report this to the concurrent-ruby developers.")
     
     RuntimeError:
       BUG: Internal monitor was not properly initialized. Please report this to the concurrent-ruby developers.
     # ./lib/concurrent-ruby/concurrent/thread_safe/util/data_structures.rb:34:in 'Concurrent::CRubySet#=='
     # ./spec/concurrent/set_spec.rb:17:in 'block (4 levels) in <module:Concurrent>'

  2) Concurrent::Set.[] when initializing with no arguments is expected to be empty
     Failure/Error: monitor or raise("BUG: Internal monitor was not properly initialized. Please report this to the concurrent-ruby developers.")
     
     RuntimeError:
       BUG: Internal monitor was not properly initialized. Please report this to the concurrent-ruby developers.
     # ./lib/concurrent-ruby/concurrent/thread_safe/util/data_structures.rb:34:in 'Concurrent::CRubySet#empty?'
     # ./spec/concurrent/set_spec.rb:11:in 'block (4 levels) in <module:Concurrent>'

Finished in 2 minutes 31.1 seconds (files took 0.48868 seconds to load)
2157 examples, 2 failures, 12 pending

Failed examples:

rspec ./spec/concurrent/set_spec.rb:16 # Concurrent::Set.[] when initializing with arguments creates a set with the given objects
rspec ./spec/concurrent/set_spec.rb:10 # Concurrent::Set.[] when initializing with no arguments is expected to be empty

Maybe this is due to Set change in ruby4_0 like
https://github.com/ruby/ruby/commit/e4f85bfc311a3812de7bc2e9d068934e8b364574
but I am not sure.

Start with spec/concurrent/set_spec.rb and the failures at lines 10 and 16, then inspect lib/concurrent-ruby/concurrent/thread_safe/util/data_structures.rb:34. Reproduce the failures using the reported Ruby 4.0.0dev command and compare the behavior with the referenced Ruby Set change. Done means the affected set specs pass without the internal monitor error on Ruby 4.0.0dev.