♻️ Refactor blanket library 4

[chris-ashe]

This pull request introduces improvements to the handling and visualization of blanket and first wall geometry across the codebase, standardizes naming conventions for Darcy friction factors, and enhances output reporting for blanket properties. The most significant changes are grouped below by theme.

Geometry Calculation and Data Flow Enhancements:

• The hydraulic diameter and bend radii for blanket channels are now calculated and stored in fwbs_variables during the run methods of both the DCLL and HCPB blanket classes, improving consistency and data availability for downstream use.

• The first wall (Fw) class now instantiates BlanketLibrary and uses its calculate_pipe_bend_radius method to set the bend radii for first wall channels, centralizing geometry logic.
  Visualization Improvements:

• The plotting routine in plot_proc.py now includes a detailed poloidal cross-section of the blanket and first wall, with labeled axes, grid, and lines marking the major radius, blanket half height, and midplane for improved interpretability.

Output Reporting Enhancements:

• The blanket half height (dz_blkt_half) is now explicitly written to output files in both the blanket library and HCPB modules, ensuring this key geometric parameter is available in results.
  Documentation and Standards:

• Added a new section to the development standards documentation specifying that Darcy friction factor variables should use the darcy_frict_ prefix, promoting consistent naming conventions.

Data Structure Import Correction:

• Updated hcpb.py to import blanket_library variables from the correct module, ensuring data consistency.## Description

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 12.00000% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.95%. Comparing base (633a49e) to head (3210187).
⚠️ Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
process/io/plot_proc.py	0.00%	13 Missing ⚠️
process/hcpb.py	20.00%	4 Missing ⚠️
process/dcll.py	0.00%	3 Missing ⚠️
process/blanket_library.py	0.00%	1 Missing ⚠️
process/fw.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3960      +/-   ##
==========================================
- Coverage   45.98%   45.95%   -0.03%     
==========================================
  Files         123      123              
  Lines       28550    28575      +25     
==========================================
+ Hits        13129    13132       +3     
- Misses      15421    15443      +22     

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