Caesium / libsodium-backed implementation of `hive-system.protocols/ICrypto`.

Uses parameter-object map signatures (`:crypto/*` keys) like the rest of
the crypto layer. Loads caesium lazily via `requiring-resolve` so absence
of native libsodium only fails at construction (`->caesium-crypto`).

Algorithms supported:
  :xchacha20-poly1305  — caesium.crypto.aead/xchacha20poly1305-ietf-{encrypt,decrypt}

Plain-fn DSL over `hive-system.protocols/ICrypto`. Parameter-object style:
every fn takes a single map keyed under `:crypto/*`.

Callers depend on this ns + ICrypto, never on a concrete adapter
(Tink / caesium / ...). Java interop stays inside the adapters.

Surface (key prefix `:crypto/*`):

  (aead-seal! {:crypto/adapter c :crypto/key k :crypto/plaintext pt :crypto/aad aad})
    => Result<{:crypto/ciphertext ^bytes :crypto/iv ^bytes}>

  (aead-open! {:crypto/adapter c :crypto/key k :crypto/ciphertext ct
               :crypto/iv nonce :crypto/aad aad})
    => Result<{:crypto/plaintext ^bytes}>

  (hpke-seal! {:crypto/adapter c :crypto/pubkey pub
               :crypto/plaintext pt :crypto/aad aad})
    => Result<{:crypto/ciphertext ^bytes}>

  (hpke-open! {:crypto/adapter c :crypto/keypair kp
               :crypto/ciphertext ct :crypto/aad aad})
    => Result<{:crypto/plaintext ^bytes}>

  (sha256 {:crypto/adapter c :crypto/data ^bytes})
    => Result<{:crypto/hash ^bytes :crypto/algorithm :sha256}>

  (random-key)              -> 32-byte ^bytes  (XChaCha20 key)
  (random-nonce)             -> 24-byte ^bytes  (XChaCha20 nonce)
  (random-x25519-keypair)    -> {:public 32B :private 32B}

Default `:crypto/algorithm` keys are filled in by each fn (caller may
override via the same key in the input map).

Pure-Java HKDF-SHA256 (RFC 5869). Shared by ICrypto adapters so that
`crypto-derive-key` returns byte-identical bytes regardless of which
adapter resolves the call.

Composed from `javax.crypto.Mac` HMAC-SHA256 — no native dependency.

Macro sugar for AEAD ceremonies built on `hive-system.crypto.core`.

Provided as an opt-in convenience layer on top of the fn DSL — required
only when call sites benefit from compact nested-let composition.

Use:

  (let-aead [crypto (tink/->tink-crypto)
             key (core/random-key)
             {:keys [ciphertext iv]} (core/aead-seal! crypto key pt aad)]
    (core/aead-open! crypto key ciphertext iv aad))

`let-aead` short-circuits on the first :error Result — same semantics as
`hive-dsl.result/let-ok` — but accepts plain (non-Result) values for
adapter / key construction lines.

Tink-backed implementation of `hive-system.protocols/ICrypto`.

See `hive-system.protocols/ICrypto` for the parameter-object contract —
every op receives a single map keyed under `:crypto/*`.

Algorithms supported:
  :xchacha20-poly1305  — symmetric AEAD (subtle.XChaCha20Poly1305)
  :hpke-x25519         — RFC 9180 single-shot HPKE
                         (DHKEM-X25519 + HKDF-SHA256 + ChaCha20-Poly1305)
  :sha256              — message digest