Typed persistent store with closed-catalog column types

Primitives used: axonstore

// `axonstore` is the four-pillar persistent store. Column types map
// to SQL backend types directly (the closed v1.38.0 catalog). Note
// `Text` not `String`, `Numeric` not `Number` — `axonstore` lives at
// the data-plane layer, below the general `type` system.

axonstore PaymentVault {
    backend:     postgresql
    connection:  "postgres://payments.internal/vault"
    isolation:   serializable
    on_breach:   raise
    capability:  "payment.write"
    schema {
        txn_id:     Text primary_key
        amount:     Numeric not_null
        card_token: Text not_null
        cardholder: Text
        posted_at:  Timestamp not_null
    }
}