Fix lazy data handling in serialization, toArray, and validation

[dereuromark]

Summary

Comprehensive fixes for lazy field handling across the codebase.

Serialization & toArray fixes:

• Fix _toArrayInternal to check _lazyData before reading property values
• Ensures touchedToArray(), __serialize(), and toArray() with parameters preserve unhydrated lazy data

Template fixes:

• Fix setFromArrayFast to use array_key_exists() for lazy fields
• Fix setDefaults template to check _lazyData for lazy fields with defaults
• Fix validate() template to check _lazyData for required lazy fields
• Fix method_get_or_fail.twig to call getter (handles hydration)
• Fix method_set_or_fail.twig to clear _lazyData
• Fix method_with_or_fail.twig to clear _lazyData

Base class fixes:

• Fix base validate() to check _lazyData for required lazy fields
• Fix base setDefaults() to not overwrite lazy field data

Tests:

• Add 7 code generation tests for lazy field handling
• Add 4 runtime tests for serialization and toArray edge cases

Relates to #83

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.48%. Comparing base (3984da7) to head (8452837).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master      #90   +/-   ##
=========================================
  Coverage     83.47%   83.48%           
- Complexity     1386     1388    +2     
=========================================
  Files            40       40           
  Lines          3346     3348    +2     
=========================================
+ Hits           2793     2795    +2     
  Misses          553      553           

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