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

internal/dedup/dedup.go

@@ -35,9 +35,12 @@ func NewFilter(origin string) *Filter {
 	}
 }
 
-// Payload represents an incoming clip payload from a peer.
+// Payload represents an incoming clip payload from a peer. It carries either
+// text (Text) or a base64-encoded image (Mime + Data).
 type Payload struct {
 	Text   string `json:"text"`
+	Mime   string `json:"mime,omitempty"`
+	Data   string `json:"data,omitempty"` // base64-encoded image bytes
 	Ts     int64  `json:"ts"`
 	Origin string `json:"origin"`
 }
@@ -58,7 +61,7 @@ func (f *Filter) ShouldIgnore(p Payload) bool {
 	}
 
 	// Guard 3: ignore content we recently wrote (hash match).
-	hash := hashText(p.Text)
+	hash := hashText(p.Text + "\x00" + p.Data)
 	for _, h := range f.cache {
 		if h == hash {
 			return true
@@ -71,11 +74,21 @@ func (f *Filter) ShouldIgnore(p Payload) bool {
 // MarkWritten records that we just wrote text to the local clipboard.
 // This populates the hash cache and updates the last-write timestamp.
 func (f *Filter) MarkWritten(text string) {
+	f.markWritten(text)
+}
+
+// MarkWrittenPayload records that we just wrote a payload (text or image) to
+// the local clipboard, so echoes of it are ignored.
+func (f *Filter) MarkWrittenPayload(p Payload) {
+	f.markWritten(p.Text + "\x00" + p.Data)
+}
+
+func (f *Filter) markWritten(content string) {
 	f.mu.Lock()
 	defer f.mu.Unlock()
 
 	now := time.Now().UnixNano()
-	hash := hashText(text)
+	hash := hashText(content)
 
 	// Ring buffer: overwrite oldest entry when full.
 	if len(f.cache) < defaultCacheSize {

internal/dedup/dedup_test.go

@@ -69,6 +69,22 @@ func TestShouldAcceptNewContent(t *testing.T) {
 	}
 }
 
+func TestShouldIgnoreDuplicateImageHash(t *testing.T) {
+	f := NewFilter("machine-a")
+	f.MarkWrittenPayload(Payload{Mime: "image/png", Data: "aGVsbG8="})
+
+	p := Payload{
+		Mime:   "image/png",
+		Data:   "aGVsbG8=",
+		Ts:     time.Now().UnixNano(),
+		Origin: "machine-b",
+	}
+
+	if !f.ShouldIgnore(p) {
+		t.Error("should ignore image payload with recently written data hash")
+	}
+}
+
 func TestCacheEviction(t *testing.T) {
 	f := NewFilter("machine-a")