Tasks — crypto-curve-spec-conformance

Add **Verified by:** line to every ### Requirement: block in openspec/specs/crypto-curve/spec.md.
Add tests/spec-conformance.test.ts pinning replaceability layout, banner, Phase-0.5 consistency, native-stub state, and dangerous-tier flip gate runtime reflection.
Confirm bun scripts/openspec-conformance.ts @suaveplan/crypto-curve exits 0.
Confirm bunx turbo lint typecheck test --filter=@suaveplan/crypto-curve is green.
Confirm bunx turbo test:coverage --filter=@suaveplan/crypto-curve reports 100/100/100/100.