ADR-025 / drift item #4: remove the irpc-based actor dispatch from the vault
crate. VaultServiceHandle (Arc<std::sync::RwLock<>>) is now the sole synchronous
API. Removed: VaultProtocol enum, VaultServiceActor, VaultService wrapper,
Client<VaultProtocol> usage, irpc/irpc-derive/tokio deps, postcard dev-dep,
Serialize/Deserialize on VaultServiceError. lib.rs re-exports match the vault
README Public API. The vault is now local-only by construction with zero async
runtime dependency.
Refs: docs/architecture/crates/vault/README.md drift #4
Implements: ADR-025
# Conflicts:
# Cargo.lock
glm-5.2
7e3300e83a