Rework summary.py into a module

[je-cook]

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 12.96639% with 3289 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.67%. Comparing base (4885172) to head (04f3ff0).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/core/io/plot/summary/profiles/plasma.py	6.15%	366 Missing ⚠️
process/core/io/plot/summary/api.py	13.11%	265 Missing ⚠️
process/core/io/plot/summary/plasma/physics.py	7.72%	251 Missing ⚠️
process/core/io/plot/summary/geometry/poloidal.py	11.71%	211 Missing ⚠️
process/core/io/plot/summary/profiles/misc.py	7.92%	186 Missing ⚠️
process/core/io/plot/summary/power_flow.py	4.73%	181 Missing ⚠️
process/core/io/plot/summary/reporting/misc.py	13.29%	163 Missing ⚠️
process/core/io/plot/summary/reporting/panels.py	10.05%	161 Missing ⚠️
process/core/io/plot/summary/profiles/stress.py	8.13%	158 Missing ⚠️
process/core/io/plot/summary/magnets/cs.py	10.90%	147 Missing ⚠️
... and 18 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4632      +/-   ##
==========================================
+ Coverage   49.92%   50.67%   +0.75%     
==========================================
  Files         151      180      +29     
  Lines       30236    30346     +110     
==========================================
+ Hits        15094    15377     +283     
+ Misses      15142    14969     -173     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.