feat: extract c_vector assembly and add to NetCDF export

[HopeBestWorld]

• Refactored MEEMEngine to use a dedicated assemble_c_vector helper method, abstracting the nested coefficient logic out of the main loop.
• Updated compute_hydrodynamic_coefficients to append the calculated c_vector to the mode results dictionary.
• Modified run_and_store_results to initialize, capture, and pass a full_c_vector batch array to the storage layer.
• Updated Results.store_hydrodynamic_coefficients in results.py to accept the c_vector and store it in the xarray Dataset (automatically handled by existing complex-split logic for NetCDF exports).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.40183%. Comparing base (3341c60) to head (aa5db42).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main         #75         +/-   ##
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+ Coverage   98.38833%   98.40183%   +0.01351%     
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  Files             11          11                 
  Lines           1303        1314         +11     
===================================================
+ Hits            1282        1293         +11     
  Misses            21          21                 

Flag	Coverage Δ
unit	98.40183% <100.00000%> (+0.01351%)	⬆️

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