feat(app): support local screenshot actions

internal/infrastructure/clipboard/clipboard.go

@@ -1,10 +1,10 @@
 // Package clipboard wraps golang.design/x/clipboard with lazy initialization.
 //
 // Why a wrapper:
-// - The upstream library requires a one-time clipboard.Init() call. Hiding it
-//   here keeps the application service free of init concerns.
-// - Allows future swap to a different backend (e.g. atotto/clipboard) without
-//   changing callers.
+//   - The upstream library requires a one-time clipboard.Init() call. Hiding it
+//     here keeps the application service free of init concerns.
+//   - Allows future swap to a different backend (e.g. atotto/clipboard) without
+//     changing callers.
 package clipboard
 
 import (
@@ -17,6 +17,7 @@ import (
 // Writer abstracts clipboard writes for testability.
 type Writer interface {
 	WriteText(s string) error
+	WriteImage(pngBytes []byte) error
 }
 
 type clipWriter struct {
@@ -44,3 +45,12 @@ func (w *clipWriter) WriteText(s string) error {
 	clipboard.Write(clipboard.FmtText, []byte(s))
 	return nil
 }
+
+// WriteImage replaces the clipboard contents with PNG-encoded image data.
+func (w *clipWriter) WriteImage(pngBytes []byte) error {
+	if err := w.ensureInit(); err != nil {
+		return fmt.Errorf("clipboard init: %w", err)
+	}
+	clipboard.Write(clipboard.FmtImage, pngBytes)
+	return nil
+}