Default GVEC chartmap Bcov to Boozer average

[krystophny]

Summary

• Change the GVEC chartmap converter default --Bcov mode from avg to boozer-avg.
• Add a dependency-free static test so the default stays covered even when gvec is not installed.
• Update stale profile-test wording from bit-for-bit equality to roundoff-level equality.

GVEC's Boozer evaluation computes B_theta_B and B_zeta_B on the requested Boozer grid. Using those quantities by default keeps the exported Boozer chartmap aligned with the coordinate transform used for the rest of the sampled field.

@Rykath please test this with the GVEC setup, especially the optional test_boozer_chartmap_gvec_qa path and a representative converter run.

Verification

Failing before, on origin/main:

$ python3 -c 'import ast, subprocess, sys; src=subprocess.check_output(["git","show","origin/main:tools/gvec_to_boozer_chartmap.py"], text=True); tree=ast.parse(src); default=None
for n in ast.walk(tree):
    if isinstance(n, ast.Call) and isinstance(n.func, ast.Attribute) and n.func.attr == "add_argument" and n.args and isinstance(n.args[0], ast.Constant) and n.args[0].value == "--Bcov":
        for kw in n.keywords:
            if kw.arg == "default" and isinstance(kw.value, ast.Constant): default=kw.value.value
print(f"origin/main --Bcov default: {default}")
sys.exit(0 if default == "boozer-avg" else 1)'
origin/main --Bcov default: avg
exit=1

Passing after:

$ python3 test/tests/test_gvec_chartmap_converter_static.py
PASS: GVEC converter defaults to Boozer covariant averaging

$ python3 -m py_compile tools/gvec_to_boozer_chartmap.py test/tests/test_gvec_chartmap_converter_static.py
exit=0

$ git diff --check
exit=0

$ fo test test_gvec_chartmap_converter_static
exit=0

$ fo test test_chartmap_aphi_abscissa
exit=0

Full local gate still blocked by the existing CMake/OpenMP_C configuration issue in this checkout:

$ fo check
Build: FAIL build failed: /opt/homebrew/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:654 (_FPHSA_FAILURE_MESSAGE)
...
Could NOT find OpenMP_C (missing: OpenMP_C_FLAGS OpenMP_C_LIB_NAMES)