mirgation docs and inital migration

doc.go

@@ -0,0 +1,13 @@
+// Package platform is the shared seam library for the e-commerce platform.
+//
+// It holds the small, stable interfaces and helpers that every module may
+// import WITHOUT importing another module's internals: env/config loading,
+// the AMQP and HTTP client factories, OpenTelemetry setup, graceful shutdown,
+// and the cross-module event vocabulary.
+//
+// Dependency rule: packages under platform/ import only third-party libraries
+// and other platform/ packages — never an application module. Application
+// modules depend downward onto platform. This is what keeps it a stable seam.
+//
+// See docs/platform-uniforming-plan.md for the layout and the migration order.
+package platform