Drop the irpc-based actor dispatch path from alknet-vault and convert to
direct method calls on VaultServiceHandle (drift item #4, ADR-025).
Removed:
- VaultProtocol enum with #[rpc_requests] derive from protocol.rs
- VaultServiceActor (mpsc + oneshot dispatch loop) from service.rs
- VaultService wrapper struct (only the handle is needed)
- Client<VaultProtocol> usage
- irpc, irpc-derive, tokio from [dependencies]
- postcard from [dev-dependencies]
- VaultMessage/VaultProtocol/VaultServiceActor re-exports from lib.rs
- Serialize/Deserialize derives from VaultServiceError
- postcard round-trip tests from protocol.rs
- actor tokio::test tests from service.rs
The vault now has zero async runtime dependency and zero RPC framework
dependency — it is local-only by construction. VaultServiceHandle is the
sole API: Arc<std::sync::RwLock<VaultServiceInner>> with synchronous
methods. lib.rs re-exports match the vault README Public API section.
Also fixes pre-existing clippy field_reassign_with_default warnings in
cache.rs tests so cargo clippy -- -D warnings passes.
Rename the crate from alknet-secret to alknet-vault to better reflect its
purpose as a local key vault (seed management, key derivation, encryption)
rather than a network service.
Symbol renames:
- SecretService → VaultService
- SecretServiceHandle → VaultServiceHandle
- SecretServiceActor → VaultServiceActor
- SecretServiceError → VaultServiceError
- SecretProtocol → VaultProtocol
- SecretMessage → VaultMessage
- ServiceLocked → VaultLocked
- alknet_secret → alknet_vault (crate name)
Update ADR-008 with vault access pattern: the vault is a capability source,
not a service endpoint. The CLI injects derived/decrypted material into
operation contexts — handlers never hold vault references.
