fix(feishu): don't append media tags to interactive card JSON

Appending media tags like "[attachment]" to raw JSON content produces
invalid JSON format. For interactive cards, the JSON already contains
image information and media refs are downloaded separately.

- Skip appendMediaTags for MsgTypeInteractive to preserve valid JSON
- Add test case for interactive card with images

pkg/channels/feishu/feishu_64.go

@@ -677,11 +677,18 @@ func (c *FeishuChannel) downloadResource(
 }
 
 // appendMediaTags appends media type tags to content (like Telegram's "[image: photo]").
+// For interactive cards, media tags are not appended because content is raw JSON
+// and appending would produce invalid JSON format.
 func appendMediaTags(content, messageType string, mediaRefs []string) string {
 	if len(mediaRefs) == 0 {
 		return content
 	}
 
+	// Don't append tags to JSON content (interactive cards) - would produce invalid JSON
+	if messageType == larkim.MsgTypeInteractive {
+		return content
+	}
+
 	var tag string
 	switch messageType {
 	case larkim.MsgTypeImage:

pkg/channels/feishu/feishu_64_test.go

@@ -169,6 +169,13 @@ func TestAppendMediaTags(t *testing.T) {
 			mediaRefs:   []string{"ref1"},
 			want:        "something [attachment]",
 		},
+		{
+			name:        "interactive card with images returns content unchanged",
+			content:     `{"schema":"2.0","body":{"elements":[{"tag":"img","img_key":"img_123"}]}}`,
+			messageType: "interactive",
+			mediaRefs:   []string{"ref1"},
+			want:        `{"schema":"2.0","body":{"elements":[{"tag":"img","img_key":"img_123"}]}}`,
+		},
 	}
 
 	for _, tt := range tests {