feat: native clipboard image sync (Linux, opt-in sync_images)

internal/clipboard/clipboard.go

@@ -8,6 +8,12 @@
 // Each platform file defines its own New() constructor using //go:build tags.
 package clipboard
 
+import "errors"
+
+// ErrNoImage is returned by ImageClipboard.ReadImage when the clipboard holds
+// no image data. It is a normal condition, not an error.
+var ErrNoImage = errors.New("clipboard: no image")
+
 // Clipboard is the cross-platform clipboard interface.
 type Clipboard interface {
 	// Read returns the current text content of the clipboard.
@@ -17,3 +23,15 @@ type Clipboard interface {
 	// Write sets the clipboard text content.
 	Write(text string) error
 }
+
+// ImageClipboard is an optional interface implemented by platforms that can
+// read and write image data from the clipboard. Use a type assertion to detect
+// support: `if ic, ok := cb.(clipboard.ImageClipboard); ok { ... }`.
+type ImageClipboard interface {
+	// ReadImage returns the MIME type and raw bytes of the clipboard image.
+	// It returns ErrNoImage if the clipboard holds no image.
+	ReadImage() (mime string, data []byte, err error)
+
+	// WriteImage sets the clipboard image content.
+	WriteImage(mime string, data []byte) error
+}