feat(engine): add correct mapping types for Page and Slice

[cromoteca]

Preserve Spring type information when transferring Pages and Slices, while keeping array-like access for backwards compatibility.

[codecov]

Codecov Report

❌ Patch coverage is 94.87179% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.38%. Comparing base (e482bff) to head (4322d0d).

Files with missing lines	Patch %	Lines
...generator-plugin-model/src/ModelSchemaProcessor.ts	77.77%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3981      +/-   ##
==========================================
+ Coverage   86.29%   86.38%   +0.09%     
==========================================
  Files         123      125       +2     
  Lines        8486     8588     +102     
  Branches     1302     1318      +16     
==========================================
+ Hits         7323     7419      +96     
- Misses       1140     1146       +6     
  Partials       23       23              

Flag	Coverage Δ
unittests	86.38% <94.87%> (+0.09%)	⬆️

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[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