add span wagner EOS

[EvenSol]

Further work is needed on this....

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 81.69336% with 80 lines in your changes missing coverage. Please review.

Project coverage is 43.33%. Comparing base (107b83d) to head (bfe51cb).

Files with missing lines	Patch %	Lines
...java/neqsim/thermo/util/spanwagner/SpanWagner.java	83.57%	63 Missing and 4 partials ⚠️
...eqsim/thermo/util/spanwagner/NeqSimSpanWagner.java	55.17%	9 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1359      +/-   ##
============================================
+ Coverage     43.10%   43.33%   +0.22%     
- Complexity     6787     6800      +13     
============================================
  Files           765      767       +2     
  Lines         72809    73246     +437     
  Branches       8760     8781      +21     
============================================
+ Hits          31385    31739     +354     
- Misses        39476    39550      +74     
- Partials       1948     1957       +9     

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[Copilot]

Pull Request Overview

Adds the Span-Wagner EOS implementation for pure CO₂ and a basic test scaffold.

• Introduces NeqSimSpanWagner class with methods to compute CO₂ density and various properties.
• Adds a JUnit test NeqSimSpanWagnerTest but leaves the assertion commented out.
• Provides a main method for manual verification and demonstration.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/main/java/neqsim/thermo/util/spanwagner/NeqSimSpanWagner.java	Implement Span-Wagner EOS wrapper and property retrieval
src/test/java/neqsim/thermo/util/spanwagner/NeqSimSpanWagnerTest.java	Add test method for density but missing assertion

Comments suppressed due to low confidence (1)

src/test/java/neqsim/thermo/util/spanwagner/NeqSimSpanWagnerTest.java:21

• The test method doesn't actually assert anything. Uncomment or add an assertion (e.g., assertEquals) to verify that the calculated density matches nistReference within the expected tolerance.

// assertEquals(nistReference, density, 1.0, "Span-Wagner density should match NIST reference at