[6.16] Allow servo joints to recover from position limits

[jslee02]

Fixes #1683, #1818

Summary

• cherry-picked Haidar's servo-limit commits onto to preserve authorship
• added regression plus SDF fixture to reproduce the stuck-at-limit bug
• retained existing Issue1583 regression coverage while validating the fix

Testing

• cmake --build build/default/cpp/Release --target test_Issue1583
• ./tests/regression/test_Issue1583

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.68%. Comparing base (f6742e0) to head (7c0e67d).
⚠️ Report is 1 commits behind head on release-6.16.

Files with missing lines	Patch %	Lines
dart/constraint/JointConstraint.cpp	95.45%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-6.16    #2086      +/-   ##
================================================
+ Coverage         58.64%   58.68%   +0.03%     
================================================
  Files               384      384              
  Lines             32036    32056      +20     
  Branches           3866     3870       +4     
================================================
+ Hits              18789    18812      +23     
+ Misses            13247    13244       -3     

Flag	Coverage Δ
unittests	58.68% <95.45%> (+0.03%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
dart/constraint/JointConstraint.cpp	75.96% <95.45%> (+2.25%)	⬆️

... and 1 file with indirect coverage changes

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[jslee02]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

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