Remove unused group parameter from load_scalars

[frode-aarstad]

Needed for #12784

Approach
Short description of the approach

(Screenshot of new behavior in GUI if applicable)

• 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 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')

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.38%. Comparing base (ae662b3) to head (3d26c5d).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13966      +/-   ##
==========================================
+ Coverage   91.34%   91.38%   +0.03%     
==========================================
  Files         478      482       +4     
  Lines       34067    34198     +131     
==========================================
+ Hits        31120    31252     +132     
+ Misses       2947     2946       -1     

Flag	Coverage Δ
cli-tests	36.01% <ø> (+0.04%)	⬆️
fuzz	43.61% <ø> (+0.08%)	⬆️
gui-tests	59.29% <ø> (+0.08%)	⬆️
performance-and-unit-tests	79.44% <ø> (+0.06%)	⬆️
test	46.10% <ø> (+0.06%)	⬆️

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

Files with missing lines	Coverage Δ
src/ert/storage/local_ensemble.py	96.81% <ø> (-0.12%)	⬇️

... and 14 files with indirect coverage changes

[codspeed-hq]

Merging this PR will not alter performance

✅ 36 untouched benchmarks

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_{Comparing frode-aarstad:remove-load-scalars-group (3d26c5d) with main (2a34262)}

[xjules]

this changes semantics of the test slightly. Maybe we do have a test for it though; ie. empty dataframe for load_scalars.

[xjules]

could you change it to use load_scalar_keys instead? Then the previous test name is ok

[frode-aarstad]

This a test for load_scalars() . load_scalar_keys() is tested elsewhere

[Copilot]

Pull request overview

This PR updates the storage LocalEnsemble.load_scalars API by removing the unused group parameter and adjusts unit tests/snapshots to reflect the new call pattern. This fits into ERT’s local storage layer by simplifying the scalar-loading interface and keeping tests aligned with the intended API surface.

Changes:

• Remove the group parameter from LocalEnsemble.load_scalars.
• Update unit tests to use the new load_scalars() / load_scalars(realizations=...) signature and rename tests to behavior-style names.
• Refresh snapshot outputs to match the updated test expectations.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/ert/unit_tests/storage/test_save_and_load_responses.py	Renames/updates test to validate empty DataFrame behavior using the new load_scalars() signature.
tests/ert/unit_tests/storage/test_save_and_load_parameters.py	Updates scalar-loading tests to the new API and refreshes snapshot naming/expectations.
tests/ert/unit_tests/storage/snapshots/test_save_and_load_parameters/test_that_load_scalars_returns_correct_data/0/data.csv	New snapshot for full load_scalars() output.
tests/ert/unit_tests/storage/snapshots/test_save_and_load_parameters/test_that_load_scalars_returns_correct_data/0/data_1.csv	New snapshot for load_scalars(realizations=[...]) output.
tests/ert/unit_tests/storage/snapshots/test_save_and_load_parameters/test_gen_kw_collector/0/gen_kw_collector_3.csv	Removes obsolete snapshot tied to the old test/API usage.
tests/ert/unit_tests/storage/snapshots/test_save_and_load_parameters/test_gen_kw_collector/0/gen_kw_collector_2.csv	Removes obsolete snapshot tied to the old test/API usage.
src/ert/storage/local_ensemble.py	Removes group filtering from load_scalars and simplifies the implementation accordingly.

[xjules]

Remember to squash the commits.