fix(io): materialize transition validators from dict definitions

[csentis]

What

create_machine_class_from_definition builds each Transition with cond, unless, on, before, and after from the definition — but dropped validators. So a validators entry in a dict/JSON definition was silently ignored and never ran at send(). The TransitionDict TypedDict also mistyped validators as bool.

This PR:

• threads validators through to Transition(...) in create_machine_class_from_definition;
• corrects the TransitionDict.validators annotation to the same callback-spec union as cond/unless;
• adds a regression test (tests/test_io.py::TestTransitionValidators) proving a definition-supplied validator runs and aborts on send() (the test fails without the production change).

Why

Transition.__init__ already accepts validators=; only the dict adapter wasn't passing it. Validators are the documented explicit-rejection channel (raise with a reason) — without this, dict/JSON-defined machines can't use it.

Notes

• Two-line production change + type fix; no behavior change for definitions that don't set validators.
• ruff check clean; pytest tests/test_io.py green (4 passed).

Closes #628

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (10b063f) to head (2c90212).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop      #629   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           42        42           
  Lines         4976      4976           
  Branches       812       812           
=========================================
  Hits          4976      4976           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[fgmacedo]

Hi @csentis, thanks for the careful fix and the regression test. You spotted a real bug: a validators entry in a dict/JSON definition was silently dropped, and the TransitionDict type was wrong too.

I've merged your change into develop via cherry-pick, with your authorship preserved. I couldn't merge the PR directly because the io/ module was refactored after you opened it: TransitionDict and create_machine_class_from_definition moved out of statemachine/io/__init__.py into a new statemachine/io/class_factory.py, which is what caused the conflict. Your two-line change applied cleanly to the new location, and your test came along unchanged.

One tiny follow-up on top (separate commit, not yours): the test asserted on sm.current_state, which is now deprecated in favor of configuration, so I switched it to assert "s1" in sm.configuration_values to avoid the deprecation warning.

Closing this PR since the commit is already on develop. Thanks again for the contribution!