Sync docs with current DTO features

[dereuromark]

Summary

• update docs that still describe lazy DTO fields as unsupported
• align validation and readonly guidance with the current implementation
• tone down the TypeScript docs claim so it matches the actual generator model

Verification

• composer cs-fix
• vendor/bin/phpunit

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.46%. Comparing base (7f3f4db) to head (78c5134).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #102   +/-   ##
=========================================
  Coverage     82.46%   82.46%           
  Complexity     1465     1465           
=========================================
  Files            42       42           
  Lines          3615     3615           
=========================================
  Hits           2981     2981           
  Misses          634      634           

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