move MXL retry policy to adapter

internal/adapter/mxl/retry.go

@@ -0,0 +1,25 @@
+package mxladapter
+
+import (
+	"context"
+	"errors"
+	"mxl-player/internal/source"
+)
+
+// ShouldRetry reports whether an MXL source error should start another attempt.
+func ShouldRetry(err error) bool {
+	if errors.Is(err, context.Canceled) {
+		return false
+	}
+
+	switch source.KindOf(err) {
+	case source.ErrorKindInvalidConfig:
+		return false
+	case source.ErrorKindTemporary,
+		source.ErrorKindUnavailable,
+		source.ErrorKindUnknown:
+		return true
+	default:
+		return true
+	}
+}