Assure breakthrough time is always cast to ms

[achaikou]

Issue
Resolves #13962

Approach
In theory we could fix this also in migration, but I think this issue is not so bad to warrant it.

Could backport to more previous releases, IF I figure out which release I need to backport it to...

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'just rapid-tests')

When applicable

• When screenshots are changed: Review screenshot-PR in ert-testdata,
  merge screenshot-PR in ert-testdata before merging this PR.
• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Add backport label to latest release (format: 'backport release-branch-name')

[Copilot]

Pull request overview

This PR fixes a storage-read failure for breakthrough responses by ensuring the time column is always stored with a consistent Polars datetime unit (ms), even when breakthrough time is None for a realization. This aligns breakthrough response frames across realizations so they can be concatenated/loaded without schema conflicts.

Changes:

• Ensure breakthrough time series is always cast to Datetime('ms'), including the “all None” case.
• Introduce an explicit response_schema() for breakthrough responses and assert it before returning derived frames.
• Add a regression test that saves/loads breakthrough responses across realizations with and without a breakthrough time.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/ert/config/breakthrough_config.py	Forces time to ms and asserts a stable schema for derived breakthrough responses.
tests/ert/unit_tests/config/test_breakthrough_config.py	Regression test covering stacking/loading breakthrough frames when a realization has None breakthrough time.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.94%. Comparing base (47757c5) to head (e1528d0).
⚠️ Report is 15 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #14207   +/-   ##
=======================================
  Coverage   91.93%   91.94%           
=======================================
  Files         482      484    +2     
  Lines       33516    33612   +96     
=======================================
+ Hits        30813    30903   +90     
- Misses       2703     2709    +6     

Flag	Coverage Δ
cli-tests	36.45% <40.00%> (-0.03%)	⬇️
fuzz	44.41% <40.00%> (-0.05%)	⬇️
gui-tests	58.74% <40.00%> (-0.11%)	⬇️
performance-and-unit-tests	80.94% <100.00%> (+0.05%)	⬆️
test	46.01% <40.00%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/ert/config/breakthrough_config.py	97.87% <100.00%> (+0.19%)	⬆️

... and 10 files with indirect coverage changes

[codspeed-hq]

Merging this PR will not alter performance

✅ 36 untouched benchmarks

---

_{Comparing achaikou:none_breakthrough (e1528d0) with main (a04d7f4)}

[ajaust]

Regarding the backporting. I assume backporting to the latest release should be fine (like you are doing by tagging the PR). If we realise that we need to backport the fix even further, we can add more labels later (afaik even after merging) and this will create backport PRs.

[ajaust]

I just forgot to add the comment about the test assertion to the initial review. 👴

[ajaust]

Looks good. 🎉

[scout-team-app]

Successfully created backport PR for version-24.0:

• [Backport version-24.0] Assure breakthrough time is always cast to ms #14214