A single JWK entry. Pinned to the OKP/Ed25519/EdDSA shape — other
kty values (EC, RSA, oct) deserialize but ed25519_bytes()
returns None so the engine never accidentally accepts a non-Ed25519
key.
TTL for the sv:{ppnum_id} cache entry shared between PAS (writer) and
PCS / external SDK consumers (readers). Bounds the post-break-glass
staleness window when the writer cannot preemptively invalidate.
Derive the 32-byte Ed25519 public key from a PKCS8-encoded private
PEM. Used by PAS at boot to populate /.well-known/jwks.json from the
same key material that produces issuance signatures, so issuer and
publisher cannot drift.