bug: fix sensitivity calculation for discrete time sum

[martinjrobins]

Description

Fixes #5007

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #)

Important checks:

Please confirm the following before marking the PR as ready for review:

• No style issues: nox -s pre-commit
• All tests pass: nox -s tests
• The documentation builds: nox -s doctests
• Code is commented for hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.57%. Comparing base (a7497a6) to head (c50916a).
⚠️ Report is 127 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #5008   +/-   ##
========================================
  Coverage    98.57%   98.57%           
========================================
  Files          304      304           
  Lines        23656    23661    +5     
========================================
+ Hits         23320    23325    +5     
  Misses         336      336           

☔ View full report in Codecov by Sentry.
📢 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.

[MarcBerliner]

Thanks Martin! Looks good, just some minor things. For consistency, can you add the name argument/property to the other processed variable classes?

Question (non-blocking):

• If hermite interpolation is available, can we treat dvar_dy_eval, dy_dp, and dvar_dp_eval as distinct process variables, hermite interpolate them onto self.time_integral.discrete_times, and then compute the discrete sum?

[martinjrobins]

• If hermite interpolation is available, can we treat dvar_dy_eval, dy_dp, and dvar_dp_eval as distinct process variables, hermite interpolate them onto self.time_integral.discrete_times, and then compute the discrete sum?

Yea, that would be nicer, we'd need their time derivatives though I think? I think these can be extracted during integration using IDAGetSensDky, we'd have to do that and return them as part of the solution.

[BradyPlanden]

LGTM @martinjrobins - thanks!

[MarcBerliner]

Thanks!