feat: add cluster context support in Compose with x-context extension

pkg/client/compose/context.go

@@ -0,0 +1,22 @@
+package compose
+
+import (
+	"github.com/compose-spec/compose-go/v2/types"
+)
+
+// ContextExtensionKey is the top-level Compose extension key for specifying the cluster context.
+const ContextExtensionKey = "x-context"
+
+// ClusterContext extracts the x-context value from the project's top-level extensions.
+// Returns an empty string if x-context is not set.
+func ClusterContext(project *types.Project) string {
+	v, ok := project.Extensions[ContextExtensionKey]
+	if !ok {
+		return ""
+	}
+	s, ok := v.(string)
+	if !ok {
+		return ""
+	}
+	return s
+}