chore(skills): add quantum-motion platform card (QM-class silicon spin ST qubits) #1714

What\nAdd a quantum-motion platform skill to the public library (packages/extension/skills/): the Quantum Motion hardware class — natural-Si MOS / 22 nm FDSOI gate-defined dots, singlet-triplet (S-T0) qubit encoding (the erasure-QEC architecture object), full Heisenberg exchange control, micromagnet gradient drift.\n\n## Why\nPrep for the 2026-10-05 QM meeting surfaced a physics gap: the generic spin card covers single-spin ZZ-exchange regimes but has no ST-qubit section — tonight's campaign (session-20261004-quantum-motion-prep, SPEC-20261004-QM1) had to derive the ST model, the SWAP identity, and the seed-saddle lesson from scratch. The card captures the verified results: ST exchange π-rotation at F = 0.99996 (T = 10 ns), the T = π/J_max speed-limit structure, the smooth (cliff-free) charge-noise decay, and the area-exact-seed saddle failure mode.\n\nAll physics is published-source or tonight's own verified runs — public-safe. Corporate/engagement analysis stays in vault notes, not the card.\n\n## Acceptance\n- [ ] packages/extension/skills/quantum-motion/SKILL.md with schema-valid frontmatter\n- [ ] node packages/extension/scripts/lint-skills.mjs --dir packages/extension/skills green\n- [ ] Every number carries provenance (paper arXiv id or run id)