Establish source-bound UPF local fidelity

[benjipeng]

Summary

• add literal Quantum ESPRESSO source oracles for the existing GTH local and nonlocal formulas
• preserve UPF radial quadrature and the complete PP_DIJ coupling matrix with fail-closed physics metadata
• implement content-bound UPF identities plus the compensated periodic local transform and fixed-cell local forces
• retain the rejected UZH q10 feasibility result without weakening transferability gates

Scope boundary

Periodic UPF nonlocal SCF is not enabled by this PR. Ultrasoft, PAW, spin-orbit, and nonlinear-core-correction inputs remain outside the admitted boundary.

Verification

• uv run ruff check src tests/test_dft_upf.py tests/test_dft_gth_qe_oracle.py tests/test_dft_gth_transferability.py
• 29 targeted UPF/GTH regression tests
• real vendor Si UPF parser compatibility test
• narrative and API documentation generators