revise code and change VBK_seas usage

[Rick-Methot-NOAA]

Concisely describe what has been changed/addressed in the pull request.

• Resolves [Bug]: growth discrepancy when season duration is < 1.0 (months < 12) and growth type is Gompertz-Richards #735
• [Question]: Code review for growth #156

What tests have been done?

Where are the relevant files?

<-- - [x] Test files are in the issue. --> See repo with growth test files

What tests/review still need to be done?

Is there an input change for users to Stock Synthesis?

<-- - [x] No, there was no input change. -->

Additional information (optional).

[Rick-Methot-NOAA]

I will test with big skate locally to diagnose the run failure

[Copilot]

Pull request overview

This pull request refactors the growth calculation code in Stock Synthesis, focusing on improving variable naming clarity and revising how seasonal growth adjustments (VBK_seas) are applied. The changes address issues #735 and #156.

Key changes:

• Renamed growth-related variables for clarity (VBK_temp → VBK_work, VBK_temp2 → VBK_by_seas)
• Restructured growth type handling with improved switch statement organization
• Modified VBK_seas usage by removing seasdur(s) multipliers in growth calculations
• Added documentation comments explaining VBK variable purposes
• Removed preprocessor conditionals (#ifdef DO_ONCE) in favor of runtime checks

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[e-perl-NOAA]

@Rick-Methot-NOAA I had copilot review the PR in case there was anything that it might be able to easily identify anything the that might cause the big skate model to fail. There were some suggestions it gave which didn't matter and I closed those but it might be worth looking at some of the other suggestions it made. If they are wrong or you don't agree, feel free to just click the "Resolve conversation" button and they will go away.

[Rick-Methot-NOAA]

now investigating the failure with growth time-vary