Define adapter interfaces and fake implementations

internal/adapters/storage/archive.go

@@ -0,0 +1,29 @@
+// Package storage declares archive/storage backend adapter boundaries.
+package storage
+
+import "context"
+
+// Backend is the adapter boundary for archive/storage operations.
+type Backend interface {
+	Archive(ctx context.Context, req ArchiveRequest) (ArchiveResult, error)
+}
+
+// ArchiveItem describes one item to archive.
+type ArchiveItem struct {
+	Kind      string
+	LocalPath string
+	RemoteKey string
+}
+
+// ArchiveRequest describes one archive operation.
+type ArchiveRequest struct {
+	SessionID    string
+	ManifestPath string
+	Items        []ArchiveItem
+}
+
+// ArchiveResult describes archive operation output.
+type ArchiveResult struct {
+	Archived []ArchiveItem
+	Metadata map[string]any
+}