source_cell: give stateless private helpers a real interface instead of friendship

[Critsium-xy]

source_cell: give stateless private helpers a real interface instead of friendship

The #define private public cleanup has been reaching for
friend class XxxTest; whenever a test calls a private method. For part of
those methods that is the wrong tool: measuring them shows they never touch
this at all. A function that uses only its arguments is not a member function,
and a test calling it needs neither friendship nor a wrapper -- it needs the
function to be declared where it can be called.

Of the ten private methods this series has granted friendship for, six use no
object state. This change deals with all six, and two of them turn out not to
need to exist.

Two are dead code kept reachable only by a test

Magnetism::judge_parallel has no caller anywhere and is a character-for-
character duplicate of the free function unitcell::judge_parallel in
cal_ux.h, which is used (cal_ux.cpp) and is already covered by
UcellTest.JudgeParallel. The duplicate, its friend class MagnetismTest; and
the fixture wrapper are removed.

Coverage improves rather than shrinks: MagnetismTest.JudgeParallel checked
both a parallel and a non-parallel pair, while UcellTest.JudgeParallel only
checked the parallel one. The negative case moves to UcellTest, so the
surviving, actually-used function is now better tested than before.

Pseudopot_upf::trimend likewise has no production caller -- only its own
definition and a test reaching through the access hack. Removed, along with the
half of ReadPPTest.Trim that exercised it.

Four become plain functions

set_pseudo_type, trim, setqfnew and complete_default_h move out of
Pseudopot_upf into namespace pseudopot, declared in read_pp.h. Their
bodies are unchanged; the internal callers (init_pseudo_reader,
complete_default, the qfunc expansion in read_pp.cpp, and getnameval in
read_pp_upf201.cpp) gain the qualifier. Six forwarding wrappers disappear from
read_pp_test.cpp and pseudo_nc_test.cpp, which now call the functions
directly.

This is better than the alternatives it replaces: unlike friend, it grants no
special access to anyone; unlike making them public members, it does not widen
the interface of Pseudopot_upf at all.

What this does not achieve

No Pseudopot_upf friend declaration is removed. All four fixtures still need
read_pseudo_upf201, which writes thirteen members and is genuinely stateful.
The only friendship eliminated here is Magnetism's, and only because its sole
private member was the dead duplicate.

The remaining four friended methods -- read_pseudo_upf201 (13 this->),
Numerical_Orbital_Lm::cal_kradial (18) and plot (26), and
Grid::setMemberVariables (34) -- cannot be handled this way: as free functions
they would take either the whole object, which gains nothing, or a dozen
parameters, which is worse. Extracting a pure computational core from them is a
production refactor and belongs in its own proposal, not in a test-access
cleanup.

Verification

Linux, cmake -B build -G Ninja -DBUILD_TESTING=ON -DENABLE_LCAO=ON -DENABLE_MPI=ON -DENABLE_OPENMP=ON:

• Build: the only failing target is
  source_lcao/module_lr/.../lr_io_krlist.cpp.o, on
  ri_util.h: RI/global/Array_Operator.h: No such file or directory. That is
  pre-existing on develop in an environment without LibRI headers (from
  Refactor LR_IO function and add test case 58_KP_LR_BSE #7849); this PR touches neither file. Every other target compiles, and the
  compiler reported no member-access error anywhere, which is the direct
  confirmation that these six functions really were stateless.
• All twelve affected tests pass: MODULE_CELL_read_pp,
  MODULE_CELL_pseudo_nc, MODULE_CELL_atom_pseudo, MODULE_CELL_atom_spec,
  MODULE_CELL_magnetism and the seven MODULE_CELL_unitcell_test* variants.
• agent_governance_check.py --base upstream/develop --head HEAD: 0 errors.

No INPUT parameter and no user-visible behaviour changed, so
docs/parameters.yaml and docs/advanced/input_files/input-main.md need no
update.

Co-Authored-By: Claude Opus 5 (1M context) noreply@anthropic.com

🤖 Generated with Claude Code