Module pairing 

DM Pairing Protocol

Implements a challenge-response device pairing protocol for authenticated direct-message communication between the agent and trusted devices.

The flow:

1. Device requests pairing via PairingManager::create_challenge.
2. Agent presents a challenge (nonce) to the user.
3. Device computes an HMAC response over the nonce using the shared secret.
4. Agent verifies the response via PairingManager::verify_response.
5. On success the device is added to the paired-devices list.

Structs

DeviceIdentity

Identity of a paired device.

PairingChallenge

A challenge issued to a device during the pairing flow.

PairingManager

Manages the device pairing lifecycle: challenge creation, verification, device listing, and revocation.

PairingResponse

A device’s response to a pairing challenge.

TotpVerifier

TOTP-style code generator and verifier (time-based one-time password).

Enums

PairingResult

Outcome of a pairing attempt.