feat(server): add persistence types and ClientRecord structure

- Add ClientRecord, ClientSession, ServerRegistry interfaces
- Add serialization helpers for persistent storage
- Add state check functions (isPairable, canAuthenticate, etc.)
- Export persistence types from plugin index.ts

plugin/core/persistence.ts

@@ -0,0 +1,250 @@
+/**
+ * Yonexus Server - Persistence Types
+ * 
+ * Defines the persistent record structures for client registry and state management.
+ * Based on PLAN.md section 6 and 12.
+ */
+
+/**
+ * Client pairing status
+ */
+export type PairingStatus = "unpaired" | "pending" | "paired" | "revoked";
+
+/**
+ * Client liveness status
+ */
+export type ClientLivenessStatus = "online" | "offline" | "unstable";
+
+/**
+ * Pairing notification delivery status
+ */
+export type PairingNotifyStatus = "pending" | "sent" | "failed";
+
+/**
+ * Security window entry for nonce tracking
+ */
+export interface NonceEntry {
+  /** The nonce value */
+  readonly nonce: string;
+  /** UTC unix timestamp when the nonce was used */
+  readonly timestamp: number;
+}
+
+/**
+ * Security window entry for handshake attempt tracking
+ */
+export interface HandshakeAttemptEntry {
+  /** UTC unix timestamp of the attempt */
+  readonly timestamp: number;
+}
+
+/**
+ * Persistent client record stored by Yonexus.Server
+ * 
+ * This structure represents the durable trust state for a client.
+ * Rolling security windows (recentNonces, recentHandshakeAttempts) may be
+ * cleared on server restart as per v1 semantics.
+ */
+export interface ClientRecord {
+  /** Unique client identifier */
+  readonly identifier: string;
+
+  /** Client's public key (Ed25519 or other) - stored after pairing */
+  publicKey?: string;
+
+  /** Shared secret issued after successful pairing */
+  secret?: string;
+
+  /** Current pairing status */
+  pairingStatus: PairingStatus;
+
+  /** Pairing code (only valid when pairingStatus is "pending") */
+  pairingCode?: string;
+
+  /** Pairing expiration timestamp (UTC unix seconds) */
+  pairingExpiresAt?: number;
+
+  /** When the pairing notification was sent (UTC unix seconds) */
+  pairingNotifiedAt?: number;
+
+  /** Status of the pairing notification delivery */
+  pairingNotifyStatus?: PairingNotifyStatus;
+
+  /** Current liveness status (may be stale on restart) */
+  status: ClientLivenessStatus;
+
+  /** Last heartbeat received timestamp (UTC unix seconds) */
+  lastHeartbeatAt?: number;
+
+  /** Last successful authentication timestamp (UTC unix seconds) */
+  lastAuthenticatedAt?: number;
+
+  /**
+   * Recent nonces used in authentication attempts.
+   * This is a rolling window that may be cleared on restart.
+   */
+  recentNonces: NonceEntry[];
+
+  /**
+   * Recent handshake attempt timestamps.
+   * This is a rolling window that may be cleared on restart.
+   */
+  recentHandshakeAttempts: number[];
+
+  /** Record creation timestamp (UTC unix seconds) */
+  readonly createdAt: number;
+
+  /** Record last update timestamp (UTC unix seconds) */
+  updatedAt: number;
+}
+
+/**
+ * In-memory session state (not persisted)
+ * 
+ * Represents an active or pending WebSocket connection.
+ */
+export interface ClientSession {
+  /** Client identifier */
+  readonly identifier: string;
+
+  /** WebSocket connection instance */
+  readonly socket: unknown; // Will be typed as WebSocket when implementing transport
+
+  /** Whether the client is currently authenticated */
+  isAuthenticated: boolean;
+
+  /** Session start timestamp (UTC unix seconds) */
+  readonly connectedAt: number;
+
+  /** Last activity timestamp (UTC unix seconds) */
+  lastActivityAt: number;
+}
+
+/**
+ * Server registry state
+ * 
+ * Contains both persistent and in-memory state for all clients.
+ */
+export interface ServerRegistry {
+  /** Persistent client records keyed by identifier */
+  clients: Map<string, ClientRecord>;
+
+  /** Active WebSocket sessions keyed by identifier */
+  sessions: Map<string, ClientSession>;
+}
+
+/**
+ * Serialized form of ClientRecord for JSON persistence
+ */
+export interface SerializedClientRecord {
+  identifier: string;
+  publicKey?: string;
+  secret?: string;
+  pairingStatus: PairingStatus;
+  pairingCode?: string;
+  pairingExpiresAt?: number;
+  pairingNotifiedAt?: number;
+  pairingNotifyStatus?: PairingNotifyStatus;
+  status: ClientLivenessStatus;
+  lastHeartbeatAt?: number;
+  lastAuthenticatedAt?: number;
+  createdAt: number;
+  updatedAt: number;
+  // Note: recentNonces and recentHandshakeAttempts are intentionally
+  // excluded from persistent serialization - they are cleared on restart
+}
+
+/**
+ * Server persistence file format
+ */
+export interface ServerPersistenceData {
+  /** Format version for migration support */
+  version: number;
+
+  /** Server-side client records */
+  clients: SerializedClientRecord[];
+
+  /** Persistence timestamp (UTC unix seconds) */
+  persistedAt: number;
+}
+
+/**
+ * Create a new empty client record
+ */
+export function createClientRecord(identifier: string): ClientRecord {
+  const now = Math.floor(Date.now() / 1000);
+  return {
+    identifier,
+    pairingStatus: "unpaired",
+    status: "offline",
+    recentNonces: [],
+    recentHandshakeAttempts: [],
+    createdAt: now,
+    updatedAt: now
+  };
+}
+
+/**
+ * Convert a ClientRecord to its serialized form (for persistence)
+ */
+export function serializeClientRecord(record: ClientRecord): SerializedClientRecord {
+  return {
+    identifier: record.identifier,
+    publicKey: record.publicKey,
+    secret: record.secret,
+    pairingStatus: record.pairingStatus,
+    pairingCode: record.pairingCode,
+    pairingExpiresAt: record.pairingExpiresAt,
+    pairingNotifiedAt: record.pairingNotifiedAt,
+    pairingNotifyStatus: record.pairingNotifyStatus,
+    status: record.status,
+    lastHeartbeatAt: record.lastHeartbeatAt,
+    lastAuthenticatedAt: record.lastAuthenticatedAt,
+    createdAt: record.createdAt,
+    updatedAt: record.updatedAt
+  };
+}
+
+/**
+ * Deserialize a client record and initialize rolling windows
+ */
+export function deserializeClientRecord(
+  serialized: SerializedClientRecord
+): ClientRecord {
+  return {
+    ...serialized,
+    recentNonces: [], // Rolling windows cleared on restart
+    recentHandshakeAttempts: []
+  };
+}
+
+/**
+ * Check if a client record is in a pairable state
+ */
+export function isPairable(record: ClientRecord): boolean {
+  return record.pairingStatus === "unpaired" || record.pairingStatus === "revoked";
+}
+
+/**
+ * Check if a client record has a pending pairing that may have expired
+ */
+export function hasPendingPairing(record: ClientRecord): boolean {
+  return record.pairingStatus === "pending" && record.pairingCode !== undefined;
+}
+
+/**
+ * Check if a pending pairing has expired
+ */
+export function isPairingExpired(record: ClientRecord, now: number = Date.now() / 1000): boolean {
+  if (!hasPendingPairing(record) || record.pairingExpiresAt === undefined) {
+    return false;
+  }
+  return now > record.pairingExpiresAt;
+}
+
+/**
+ * Check if a client is ready for authentication (has secret and is paired)
+ */
+export function canAuthenticate(record: ClientRecord): boolean {
+  return record.pairingStatus === "paired" && record.secret !== undefined && record.publicKey !== undefined;
+}