fix: syntax error in class diagrams with nested generics

[Sigmabrogz]

Summary

Fixes the syntax error when attempting to define a class with an inline nested generic type and inline type definitions in the classchart.html demo file.

Problem

Closes #7480

The parser threw a "Syntax error in text" message in the classchart.html demo. Specifically:

• The parser could not handle the space-separated class alias on a single line.
• The closing nested generics (~~) were misinterpreted as markdown strike-through tokens.
• Method return types were missing colons (: T), violating the Langium parser requirements.

Solution

• Changed class People List~List~Person~~ to a standard block definition.
• Added a whitespace between nested tildes (~ ~) to prevent the strike-through tokenization error.
• Added missing colons to method return types (+getItem() : T).

Testing

• Modified the demo file as suggested in the issue.
• The demo file's code is strictly HTML text that is parsed by Mermaid. This fixes the immediate syntax failure.

Checklist

• Code builds without errors
• Tests pass
• Dependencies added to package.json

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Latest commit: bd57234

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commit: bd57234

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.52%. Comparing base (277c496) to head (bd57234).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #7489   +/-   ##
=======================================
  Coverage     3.52%   3.52%           
=======================================
  Files          509     508    -1     
  Lines        49790   49779   -11     
  Branches       785     785           
=======================================
  Hits          1754    1754           
+ Misses       48036   48025   -11     

Flag	Coverage Δ
unit	3.52% <ø> (+<0.01%)	⬆️

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Build	Status	Details	Updated (UTC)
default (Inspect)	✅ No changes detected	-	Mar 15, 2026, 4:15 AM