fix(abacus): transform forces for left-handed SCF cells

[SchrodingersCattt]

Fixes #1061.

ABACUS normalizes left-handed STRU cells by reflecting the cell and Cartesian coordinates. Propagate that reflection to SCF force vectors so coordinates and forces remain in the same spatial representation. Add a regression test covering a left-handed cell with nonzero forces.

Tests: ABACUS test suite and ruff checks pass.

Summary by CodeRabbit

• Bug Fixes
  • Corrected force handling when reading ABACUS results that use a left-handed cell. Forces now stay consistent with the corrected cell orientation, avoiding sign errors in parsed data.
  • Results with right-handed cells are unaffected, and files without force data continue to be read without changes.

[codspeed]

Merging this PR will not alter performance

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✅ 2 untouched benchmarks

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_{Comparing SchrodingersCattt:fix/abacus-scf-left-handed (f116b43) with master (520a909)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.09%. Comparing base (520a909) to head (f116b43).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1065   +/-   ##
=======================================
  Coverage   88.08%   88.09%           
=======================================
  Files          91       91           
  Lines        9685     9690    +5     
=======================================
+ Hits         8531     8536    +5     
  Misses       1154     1154           

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Important

Review skipped

Review was skipped as selected files did not have any reviewable changes.

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📥 Commits

Reviewing files that changed from the base of the PR and between 520a909 and f3f354c.

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📒 Files selected for processing (3)

• dpdata/formats/abacus/scf.py
• dpdata/formats/abacus/stru.py
• tests/test_abacus_pw_scf.py

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📝 Walkthrough

Walkthrough

The STRU reader can report when it reflects a left-handed cell. The SCF reader uses that flag to negate collected forces. A regression test checks the parsed coordinates and forces.

Changes

ABACUS SCF force transformation

Layer / File(s)	Summary
Expose the cell reflection flag dpdata/formats/abacus/stru.py	get_frame_from_stru records whether the cell has a negative determinant. It can return the parsed data with that flag, while its default return remains data-only.
Apply the reflection to SCF forces dpdata/formats/abacus/scf.py, tests/test_abacus_pw_scf.py	When the structure reader reports a flipped cell, get_frame negates collected forces. The regression test checks the parsed coordinates and forces against the methane reference.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Suggested reviewers: pxlxingliang

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Merge Risk: ⚪ Minimal · up to f3f35

The force transformation matches the coordinate correction for left-handed cells, so no material merge-blocking risk is identified.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: transforming forces for left-handed ABACUS SCF cells.
Linked Issues check		Issue #1061 requires force transformation when ABACUS applies the left-handed-cell correction. The PR records whether get_frame_from_stru flips the cell and negates available SCF forces in `get_fram…
Out of Scope Changes check		The changes are limited to the STRU flip-status propagation, conditional SCF force negation, and a regression test. These changes directly support issue #1061. No unrelated behavior or files are ident…

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