RandomRotation: stale ase.constraints stress import breaks on ASE 3.29 (+ in-place mutation of input atoms)

[sirmarcel]

RandomRotation.random_map in marathon/grain/transforms/transforms.py has two issues, found while using rotational augmentation with a magnetic model (ASE 3.29.0).

1. Stale ASE import (breaks augmentation with Voigt-6 stress)

Line ~134:

from ase.constraints import (
    full_3x3_to_voigt_6_stress,
    voigt_6_to_full_3x3_stress,
)

These were moved to ase.stress in recent ASE (3.29). This raises ImportError: cannot import name 'full_3x3_to_voigt_6_stress' from 'ase.constraints' whenever a sample carries stress in Voigt-6 shape (6,) (the stress.shape == (6,) branch).

Note: marathon/grain/data_source/properties.py::convert_stress already imports these correctly from ase.stress — so the fix is just to match that here.

2. In-place mutation of the input atoms' calculator (minor)

Line ~126:

results = atoms.calc.results
if "forces" in self.keys and "forces" in results:
    results["forces"] = np.einsum("ab,ib->ia", R, F)

results aliases the input atoms' calc.results, so the rotation is written back onto the source atoms before atoms.copy(). Harmless in a grain pipeline (fresh atoms per read), but surprising and a footgun. Suggest results = dict(atoms.calc.results) first.

Repro

from marathon.grain import RandomRotation
import numpy as np
# atoms with a Voigt-6 stress in its SinglePointCalculator
RandomRotation().random_map(atoms, np.random.default_rng(0))  # ImportError under ASE 3.29

Fix: import full_3x3_to_voigt_6_stress, voigt_6_to_full_3x3_stress from ase.stress, and copy results before mutating.