feat(gateway): add node capability negotiation foundation

src/gateway/protocol.ts

@@ -8,6 +8,16 @@ export interface GatewayRequest {
   params?: Record<string, unknown>;
 }
 
+export const GATEWAY_PROTOCOL_VERSION = 1;
+
+export interface NodeRegisterParams {
+  connectionId: string;
+  nodeId: string;
+  role: string;
+  protocolVersion: number;
+  capabilities: string[];
+}
+
 // ── Server → Client ────────────────────────────────────────────
 
 export interface GatewayResponse {
@@ -129,6 +139,37 @@ export function parseMessage(raw: string): GatewayRequest | null {
   }
 }
 
+export function parseNodeRegisterParams(params: unknown): NodeRegisterParams | null {
+  if (!params || typeof params !== 'object') {
+    return null;
+  }
+  const p = params as Record<string, unknown>;
+  if (typeof p.connectionId !== 'string' || !p.connectionId.trim()) {
+    return null;
+  }
+  if (typeof p.nodeId !== 'string' || !p.nodeId.trim()) {
+    return null;
+  }
+  if (typeof p.role !== 'string' || !p.role.trim()) {
+    return null;
+  }
+  if (typeof p.protocolVersion !== 'number' || !Number.isFinite(p.protocolVersion) || p.protocolVersion < 1) {
+    return null;
+  }
+  const capabilitiesRaw = p.capabilities;
+  if (!Array.isArray(capabilitiesRaw) || !capabilitiesRaw.every((entry) => typeof entry === 'string')) {
+    return null;
+  }
+
+  return {
+    connectionId: p.connectionId,
+    nodeId: p.nodeId,
+    role: p.role,
+    protocolVersion: Math.floor(p.protocolVersion),
+    capabilities: capabilitiesRaw,
+  };
+}
+
 export function makeResponse(id: number, result: unknown): GatewayResponse {
   return { id, result };
 }