Tasks — crypto-hash-spec-conformance

Add **Verified by:** line to every ### Requirement: block in openspec/specs/crypto-hash/spec.md.
Add tests/spec-conformance.test.ts pinning package-identity and per-primitive replaceability layout scenarios.
Confirm bun scripts/openspec-conformance.ts @suaveplan/crypto-hash exits 0.
Confirm bunx turbo lint typecheck test --filter=@suaveplan/crypto-hash is green.
Confirm bunx turbo test:coverage --filter=@suaveplan/crypto-hash reports 100/100/100/100.