♻️ Refactor Bruner div heat split

[chris-ashe]

Description

This pull request introduces significant improvements to the plasma exhaust modeling and visualization in PROCESS. The main changes include the addition of new documentation for plasma exhaust physics, refactoring and renaming of variables related to divertor power splits for clarity and consistency, and the implementation of new plotting functions to visualize separatrix power splits and Brunner model power sharing. These updates enhance both the usability and accuracy of the plasma exhaust modeling, while also improving the documentation and user interface.

Plasma Exhaust Modeling and Documentation:

• Added a comprehensive new documentation page (plasma_exhaust.md) describing separatrix power, divertor protection metrics, and the Brunner model for power splits.
• Added Plasma Exhaust to the navigation in mkdocs.yml for easier access to the new documentation.

Variable Renaming and Data Structure Updates:

• Refactored all instances of f_p_div_lower to f_p_div_lower_separatrix and updated related obsolete variable mappings for clarity and consistency in input, scan, and obsolete variable code.
• Expanded PhysicsData to include explicit variables for separatrix power splits and target powers (e.g., f_p_div_inboard_separatrix, p_div_lower_inboard_separatrix_mw, etc.), replacing ambiguous or legacy variable names.

Visualization and Plotting Enhancements:

• Added two new plotting functions: one for visualizing Brunner divertor power splits as a stack plot, and another for displaying separatrix power splits as a bar chart, both integrated into the summary plotting workflow.
• Ensured that these new visualizations are included in the plasma exhaust summary page for improved user analysis.

Large tokamak

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Codebase Maintenance:

• Updated imports and references to support new models and maintain code clarity, including importing DivertorNumberModels and PlasmaExhaust where required. [1] [2]

These changes collectively improve the clarity, maintainability, and scientific accuracy of the plasma exhaust modeling in PROCESS, while also enhancing the user experience through better documentation and visualization.

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 34.53608% with 127 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.26%. Comparing base (c0ae5b2) to head (7769f8a).

Files with missing lines	Patch %	Lines
process/core/io/plot/summary.py	4.76%	80 Missing ⚠️
process/models/physics/exhaust.py	55.17%	26 Missing ⚠️
process/models/physics/physics.py	0.00%	16 Missing ⚠️
process/models/physics/scrape_off_layer.py	0.00%	4 Missing ⚠️
process/models/build.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4511      +/-   ##
==========================================
- Coverage   49.32%   49.26%   -0.07%     
==========================================
  Files         150      150              
  Lines       29802    29940     +138     
==========================================
+ Hits        14700    14750      +50     
- Misses      15102    15190      +88     

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[je-cook]

this name is far too long to be used in the function (hence the formatting nightmare), fine if you want it for input but please rename it to something more useable inside the function