SentinelPass IPC protocol contract.
This crate is the narrow, stable surface that daemon clients embed:
message types, the authentication envelope, wire framing (length-prefixed
frames, 64 KiB cap), platform transports (client side), token file
management, and [IpcClient].
Stability rules:
- Every wire type must deserialize old payloads (serde defaults for new fields; unknown fields are ignored by serde).
- Framing and Windows AES-256-GCM frame format never change byte layout.
Server-side types (listeners, the request dispatcher) intentionally live
in sentinelpass-core, not here.