Collect pieces for SSP 2024/ScenarioMIP

[khaeru]

This PR is to track the working branch ssp-dev, which exists to help with work on the SSP 2024/ScenarioMIP project by collecting or pointing to all the code that is actually used to execute the workflow.

The goal is to be complete and up-to-date as possible for that purpose; other aspects (code quality, cleanliness, or readiness for main) are less important.

How to use

• Per Collect pieces for SSP 2024/ScenarioMIP workflows #234, it is not necessary to use this branch. If you can make an atomic PR for individual, small changes, do that first. This branch will be regularly rebased on latest main, so will include those updates.
• Update this branch, e.g. by cherry-picking commits or copying code from various other working branches used for this project.
• Make a PR that targets into this branch, and then request that someone review it. Continue work on this branch, rather than the PR source branch.

How to review

TBD: this PR may not eventually be merged.

PR checklist

• Continuous integration checks all ✅ TBD if this will be required.
• Add or expand tests; coverage checks both ✅
• Add, expand, or update documentation.
• Update doc/whatsnew.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.5%. Comparing base (f6de7bb) to head (526f5cb).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #235   +/-   ##
=====================================
  Coverage   65.5%   65.5%           
=====================================
  Files        204     204           
  Lines      15822   15822           
=====================================
  Hits       10378   10378           
  Misses      5444    5444