feat(eventmodeling): enforce Event Modeling connection invariants via Langium validator

[yordis]

📑 Summary

Adds a Langium semantic validator to the Event Modeling diagram that enforces the directional connection invariants defined by the Event Modeling methodology.

📏 Design Decisions

Event Modeling defines a strict information flow between entity types:

screen/ui → command → event → read model → processor/screen

Without enforcement, the grammar silently accepted connections that violate these invariants. Most notably, an event flowing directly into a processor (bypassing a read model), which is not a valid pattern in Event Modeling.

The validator enforces the following rules via Langium's ValidationRegistry, reporting errors on invalid ->> source references:

Target type	Allowed sources
event	command only
read model	event only
processor	read model only
screen	read model only
anything else	cannot source from event or read model

The check also covers the complementary direction, e.g. a command, frame cannot consume an event as its source. Ensuring events flow exclusively into read models, and read models flow exclusively into processors or screens.

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🦋 Changeset detected

Latest commit: d50c423

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[adymitruk]

Screen is a loose term for human interface which can be an email, voice command or voice feedback.

[yordis]

@pbrolin47 These changes are based on @adymitruk (the author of eventmodeling 😃) to make sure the diagram is proper.

As @adymitruk mentioned above, screen isn't the language we use, normally it would be ui since the ui could be a non-graphical interface as well.

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commit: d50c423

[codecov]

Codecov Report

❌ Patch coverage is 1.72414% with 57 lines in your changes missing coverage. Please review.
✅ Project coverage is 3.33%. Comparing base (abecf56) to head (d50c423).
⚠️ Report is 75 commits behind head on develop.

Files with missing lines	Patch %	Lines
...language/eventmodeling/event-modeling-validator.ts	1.85%	53 Missing ⚠️
...ckages/parser/src/language/eventmodeling/module.ts	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #7588      +/-   ##
==========================================
- Coverage     3.33%   3.33%   -0.01%     
==========================================
  Files          536     537       +1     
  Lines        56240   56298      +58     
  Branches       820     821       +1     
==========================================
+ Hits          1877    1878       +1     
- Misses       54363   54420      +57     

Flag	Coverage Δ
unit	3.33% <1.72%> (-0.01%)	⬇️

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

Files with missing lines	Coverage Δ
...ckages/parser/src/language/eventmodeling/module.ts	3.84% <0.00%> (-0.70%)	⬇️
...language/eventmodeling/event-modeling-validator.ts	1.85% <1.85%> (ø)

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Build	Status	Details	Updated (UTC)
default (Inspect)	👍 Changes approved	1 changed	Apr 7, 2026, 7:52 PM

[pbrolin47]

@yordis Thanks for this PR.

[yordis]

@pbrolin47 any opportunity to take this one before the official release cause the situation to be a breaking change? I have another PR I would like to make around the word "screen"

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