HELIX v1.0.6 — physics corrections

• Multipole misalignment applied once in multiparticle mode (was double-applied: a 1 mm offset kicked like 2 mm, tilt doubled) — now matches the envelope solver, the element semantics, and the manual; pinned by 5 regression tests
• Macrocharge convention unified across all four space-charge consumers (bit-identical by proof)
• GUI Save now surfaces writer warnings (non-relocatable decks, dropped ERROR cards)