feat(feishu): extract and download images from interactive cards

When receiving interactive card messages, extract embedded images
(img_key, src, icon_key) and download them for LLM processing.

- Add extractCardImageKeys() to recursively extract image keys from card JSON
- Support img elements (img_key, src) and icon elements (icon_key)
- Update downloadInboundMedia() to handle MsgTypeInteractive
- Add comprehensive unit tests for image extraction

Images are downloaded and stored via MediaStore, then appended to
the message content as [image: photo] tags for LLM visibility.

💘 Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

pkg/channels/feishu/common.go

@@ -178,3 +178,54 @@ func extractTextFromElement(elem any) string {
 
 	return ""
 }
+
+// extractCardImageKeys recursively extracts all image keys from a Feishu interactive card.
+// Image keys are used to download images from Feishu API.
+func extractCardImageKeys(rawContent string) []string {
+	if rawContent == "" {
+		return nil
+	}
+
+	var card map[string]any
+	if err := json.Unmarshal([]byte(rawContent), &card); err != nil {
+		return nil
+	}
+
+	var keys []string
+	extractImageKeysRecursive(card, &keys)
+	return keys
+}
+
+// extractImageKeysRecursive traverses card structure to find all image keys.
+func extractImageKeysRecursive(v any, keys *[]string) {
+	switch val := v.(type) {
+	case map[string]any:
+		// Check if this is an img element
+		if tag, ok := val["tag"].(string); ok {
+			switch tag {
+			case "img":
+				// Try img_key first (most common)
+				if imgKey, ok := val["img_key"].(string); ok && imgKey != "" {
+					*keys = append(*keys, imgKey)
+				}
+				// Also try src (alternative format)
+				if src, ok := val["src"].(string); ok && src != "" {
+					*keys = append(*keys, src)
+				}
+			case "icon":
+				// Icon elements use icon_key
+				if iconKey, ok := val["icon_key"].(string); ok && iconKey != "" {
+					*keys = append(*keys, iconKey)
+				}
+			}
+		}
+		// Recurse into all nested structures
+		for _, child := range val {
+			extractImageKeysRecursive(child, keys)
+		}
+	case []any:
+		for _, item := range val {
+			extractImageKeysRecursive(item, keys)
+		}
+	}
+}

pkg/channels/feishu/common_test.go

@@ -400,3 +400,77 @@ func TestExtractCardText(t *testing.T) {
 		})
 	}
 }
+
+func TestExtractCardImageKeys(t *testing.T) {
+	tests := []struct {
+		name    string
+		content string
+		want    []string
+	}{
+		{
+			name:    "empty content",
+			content: "",
+			want:    nil,
+		},
+		{
+			name:    "invalid JSON",
+			content: "not json",
+			want:    nil,
+		},
+		{
+			name:    "card with no images",
+			content: `{"schema":"2.0","body":{"elements":[{"tag":"markdown","content":"text"}]}}`,
+			want:    nil,
+		},
+		{
+			name:    "single image with img_key",
+			content: `{"elements":[{"tag":"img","img_key":"img_abc123"}]}`,
+			want:    []string{"img_abc123"},
+		},
+		{
+			name:    "single image with src",
+			content: `{"elements":[{"tag":"img","src":"img_xyz789"}]}`,
+			want:    []string{"img_xyz789"},
+		},
+		{
+			name:    "multiple images",
+			content: `{"elements":[{"tag":"img","img_key":"img_1"},{"tag":"div","text":{"content":"text"}},{"tag":"img","img_key":"img_2"}]}`,
+			want:    []string{"img_1", "img_2"},
+		},
+		{
+			name:    "nested image in columns",
+			content: `{"elements":[{"tag":"div","columns":[{"tag":"img","img_key":"img_col1"},{"tag":"img","img_key":"img_col2"}]}]}`,
+			want:    []string{"img_col1", "img_col2"},
+		},
+		{
+			name:    "image in action",
+			content: `{"elements":[{"tag":"action","actions":[{"tag":"img","img_key":"img_action"}]}]}`,
+			want:    []string{"img_action"},
+		},
+		{
+			name:    "icon element",
+			content: `{"elements":[{"tag":"icon","icon_key":"icon_123"}]}`,
+			want:    []string{"icon_123"},
+		},
+		{
+			name:    "complex card with text and images",
+			content: `{"header":{"title":{"content":"Title"}},"elements":[{"tag":"div","text":{"content":"Description"}},{"tag":"img","img_key":"img_main"}]}`,
+			want:    []string{"img_main"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := extractCardImageKeys(tt.content)
+			if len(got) != len(tt.want) {
+				t.Errorf("extractCardImageKeys() = %v, want %v", got, tt.want)
+				return
+			}
+			for i, v := range got {
+				if v != tt.want[i] {
+					t.Errorf("extractCardImageKeys()[%d] = %q, want %q", i, v, tt.want[i])
+				}
+			}
+		})
+	}
+}

pkg/channels/feishu/feishu_64.go

@@ -548,6 +548,16 @@ func (c *FeishuChannel) downloadInboundMedia(
 			refs = append(refs, ref)
 		}
 
+	case larkim.MsgTypeInteractive:
+		// Extract and download images embedded in interactive cards
+		imageKeys := extractCardImageKeys(rawContent)
+		for _, imageKey := range imageKeys {
+			ref := c.downloadResource(ctx, messageID, imageKey, "image", ".jpg", store, scope)
+			if ref != "" {
+				refs = append(refs, ref)
+			}
+		}
+
 	case larkim.MsgTypeFile, larkim.MsgTypeAudio, larkim.MsgTypeMedia:
 		fileKey := extractFileKey(rawContent)
 		if fileKey == "" {