Add periodic norm-conserving UPF execution

[benjipeng]

Summary

• implement full-DIJ scalar norm-conserving periodic UPF local and nonlocal operators
• dispatch periodic SCF, bands, fixed-cell forces, batching, and checkpoint identity by pseudopotential format
• fail closed for mixed formats, augmentation physics, spin-orbit terms, nonlinear core correction, and UPF stress
• deduplicate |G+k| values and batch spherical-Bessel transforms by angular channel during UPF setup
• update canonical DFT capability and roadmap documentation without widening scientific certification

Evidence

• 24 UPF tests passed; the opt-in vendor-data test is skipped by default
• source-bound Quantum ESPRESSO Si ONCV data test passed separately
• 8 focused GTH, batching, checkpoint, bands, stress, and scope regressions passed
• Ruff passed for src and the focused test surface
• 39 narrative and 69 API documentation pages generated successfully
• same-workload Si ONCV setup diagnostic improved from about 189.4 ms to 4.52 ms; warm apply remains governed by projector count and the shared device batch path

Scientific boundary

This does not certify broad UPF material transferability. SSSP 1.3 PBE precision selects Ultrasoft Mg and PAW O for MgO, which remain outside the admitted scalar norm-conserving boundary.