Add public facade value wrappers

internal/facade/source.go

@@ -0,0 +1,25 @@
+package configkit
+
+import (
+	"io"
+
+	"gitea.maximumdirect.net/eric/ConfigKit/internal/engine"
+)
+
+// Source is an opaque configuration input. Construct sources with File, Bytes,
+// Reader, or NoSource; the zero value is invalid.
+type Source struct{ value engine.Source }
+
+// File returns a source that reopens path for every load attempt.
+func File(path string) Source { return Source{value: engine.File(path)} }
+
+// Bytes snapshots data immediately.
+func Bytes(label string, data []byte) Source { return Source{value: engine.Bytes(label, data)} }
+
+// Reader returns a single-use source. Copies share the same single-use claim.
+func Reader(label string, input io.Reader) Source { return Source{value: engine.Reader(label, input)} }
+
+// NoSource explicitly selects defaults-only input.
+func NoSource() Source { return Source{value: engine.NoSource()} }
+
+func (s Source) toEngine() engine.Source { return s.value }