feat(10-01): add PAX8 typed entity barrel

- Pax8PageEnvelope<T> generic pagination envelope
- Pax8Company, Pax8Subscription, Pax8Product entity interfaces
- Pax8Order/Pax8OrderItem modeled on PAX8 Invoice/InvoiceItem fields
  (not bare Order/LineItem, which lack pricing) per 10-RESEARCH.md Pitfall 1
- escape-hatch [key: string]: unknown on each entity, matching appgate.ts convention

lib/types/pax8.ts

@@ -0,0 +1,80 @@
+/**
+ * Type definitions for the PAX8 REST API (v1) and the shapes Pulse persists.
+ * Source spec lives at `https://devx.pax8.com`.
+ *
+ * Only the slices Pulse consumes are typed — PAX8 exposes a much larger
+ * surface (marketplace/provisioning endpoints Pulse never calls as a
+ * partner/reseller). Long-tail fields fall back to the `[key: string]:
+ * unknown` escape hatch on each interface, matching lib/types/appgate.ts.
+ */
+
+// ─── API response shapes ──────────────────────────────────────────────────
+
+export interface Pax8PageEnvelope<T> {
+  content: T[];
+  page: {
+    size: number;
+    totalElements: number;
+    totalPages: number;
+    number: number;
+  };
+}
+
+export interface Pax8Company {
+  id: string;
+  name: string;
+  externalId: string | null;
+  website: string | null;
+  status: string | null;
+  city: string | null;
+  stateOrProvince: string | null;
+  postalCode: string | null;
+  country: string | null;
+  [key: string]: unknown; // escape hatch for fields not yet modeled
+}
+
+export interface Pax8Subscription {
+  id: string;
+  companyId: string;
+  productId: string;
+  quantity: number;
+  billingTerm: string | null;
+  status: string | null;
+  startDate: string | null;
+  [key: string]: unknown; // escape hatch for fields not yet modeled
+}
+
+export interface Pax8Product {
+  id: string;
+  sku: string;
+  vendorSku: string | null;
+  name: string;
+  category: string | null;
+  [key: string]: unknown; // escape hatch for fields not yet modeled
+  // NOTE: the deprecated alternate-vendor-SKU field per PAX8's own schema is intentionally omitted.
+}
+
+// Modeled on PAX8's Invoice object (not the bare Order object, which lacks
+// pricing/status) — see 10-RESEARCH.md Pitfall 1.
+export interface Pax8Order {
+  id: string;
+  companyId: string;
+  orderDate: string | null;
+  total: number | null;
+  status: string | null;
+  currencyCode: string | null;
+  [key: string]: unknown; // escape hatch for fields not yet modeled
+}
+
+// Modeled on PAX8's Invoice Item object (not the bare LineItem object,
+// which lacks pricing) — see 10-RESEARCH.md Pitfall 1.
+export interface Pax8OrderItem {
+  id: string;
+  orderId: string;
+  productId: string;
+  quantity: number;
+  price: number | null;
+  subTotal: number | null;
+  currencyCode: string | null;
+  [key: string]: unknown; // escape hatch for fields not yet modeled
+}