fix: ensure compatibility with SDKs and default environment

[erka]

This pull request improves the handling of environment selection in the environment store, especially around the use of the "default" environment key. The main change ensures that when an environment with the key "default" doesn't exist, the system will gracefully fall back to the actual default environment (even if it has a different key), which increases compatibility with SDKs and simplifies environment management.

related #4856

[dosubot]

Related Documentation

Checked 4 published document(s). No updates required.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.62%. Comparing base (bedc518) to head (5cdc66a).
⚠️ Report is 3 commits behind head on v2.

Additional details and impacted files

@@            Coverage Diff             @@
##               v2    #4857      +/-   ##
==========================================
+ Coverage   58.57%   58.62%   +0.04%     
==========================================
  Files         135      135              
  Lines       16844    16850       +6     
==========================================
+ Hits         9867     9878      +11     
+ Misses       6292     6287       -5     
  Partials      685      685              

Flag	Coverage Δ
integrationtests	33.92% <57.14%> (+0.01%)	⬆️
unittests	49.31% <100.00%> (+0.14%)	⬆️

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[markphelps]

ty!

[dosubot]

Documentation Updates

Checked 4 published document(s). No updates required.

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