fix: name the event in the delayed+internal error and let send(delay=0) override

[fgmacedo]

Why

light = Event(dark.to(lit), delay=50, internal=True) raised InvalidDefinition: Event '__event__<uuid>' cannot be both delayed and internal. The check ran in Event.__new__, before the metaclass knew the attribute name, and the 3.2.2 release-notes doctest only passed because of IGNORE_EXCEPTION_DETAIL. Separately, send("go", delay=0) could not override a declared delay, because 0 counted as "not given".

Fixes #679

What changes

• The delayed+internal error names the event by its attribute name, by its explicit id, or by the first id of an error_/done_state_/done_invoke_ prefix. This holds at the top level and inside State.Compound/State.Parallel bodies, and also for an Event(delay=..., internal=True) declared without transitions, which a nested body used to drop before checking.
• send() and raise_() default delay to None, so an explicit delay=0 overrides a declared delay on both engines. Without delay, the declared one still applies, and raise_("go") on an event declared with a delay is still InvalidDefinition.
• The SCXML/JSON/YAML <send> load-time messages are unchanged.
• In docs/releases/3.2.2.md, the doctest now checks the message with # doctest: -IGNORE_EXCEPTION_DETAIL, and the fix: honor Event(internal=True) and give internal events from outside a step the external contract #668 entry documents the delay=0 override. processing_model.md and statechart.md mention the override too.

Evidence

$ timeout 120 uv run pytest tests/test_internal_triggers.py   # before the fix, new tests only
9 failed, 44 passed   # placeholder id in 5 declaration forms; delay=0 ignored by send/raise_ on sync+async

$ timeout 180 uv run pytest -n 4 --cov=statemachine --cov-report=term-missing:skip-covered
TOTAL    6197      0   1944      0   100%
2642 passed, 25 skipped, 44 xfailed

With the event.py change reverted, the release-notes doctest fails:

+statemachine.exceptions.InvalidDefinition: Event '__event__83ad8cb8…' cannot be both delayed and internal: ...

Pre-commit (ruff, mypy, pyright, pytest) passes on the commit.

Not verified

• An Event(..., delay=50, internal=True) statement left unassigned in a class body is no longer rejected. Before, the placeholder check caught it by accident. Now the transition becomes eventless, which is what any unassigned Event(...) statement already did.
• A class rejected for delayed+internal stays in the global registry. The check now runs in the metaclass after registry.register, which is how the other metaclass-time InvalidDefinition errors already behave.
• sm.go() takes no delay argument, so there is no override to test on the bound-event call path. Only send()/raise_() were changed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (73bf57c) to head (2279678).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #683   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           53        53           
  Lines         5787      5816   +29     
  Branches       918       926    +8     
=========================================
+ Hits          5787      5816   +29     

Flag	Coverage Δ
unittests	100.00% <100.00%> (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.

[sonarqubecloud]

Quality Gate passed

Issues
5 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