chore(ci): add PHP 8.5 to CI workflows

[phil-davis]

PHP 8.5 works, so use it in CI

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.18%. Comparing base (2ad0fed) to head (37d69f3).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #139      +/-   ##
============================================
- Coverage     99.21%   99.18%   -0.03%     
  Complexity      111      111              
============================================
  Files             7        7              
  Lines           380      370      -10     
============================================
- Hits            377      367      -10     
  Misses            3        3              

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[phil-davis]

That works OK. I will leave this to merge after PHP 8.5 is officially released in Nov 2025.

https://wiki.php.net/todo/php85