fix(im): parse Drafty entities for message type classification (#31)

Favorites from Drafty messages (link/file/image/video/voice) always fell back to text because imMessageType only recognized flat file_id/url content. Derive the type from Drafty ent[] entities: LN->link, IM->image, VD->video, AU->voice, EX refined by mime. Attachments win over inline links.

server/im_http.go

@@ -8885,10 +8885,70 @@ func imMessageType(msg *types.Message) string {
 		if stringFromAny(content["url"]) != "" {
 			return "link"
 		}
+		if mtype := draftyIMMessageType(content); mtype != "" {
+			return mtype
+		}
 	}
 	return "text"
 }
 
+// draftyIMMessageType derives the semantic message type from Drafty content
+// ({"txt","fmt","ent"}), where "ent" holds entity definitions {"tp","data"}.
+// Attachment entities win over inline links; EX is refined by its mime type.
+// Returns "" when no recognized entity is present.
+func draftyIMMessageType(content map[string]any) string {
+	ents, ok := content["ent"].([]any)
+	if !ok || len(ents) == 0 {
+		return ""
+	}
+	link := ""
+	file := ""
+	for _, e := range ents {
+		ent, ok := e.(map[string]any)
+		if !ok {
+			continue
+		}
+		data, _ := ent["data"].(map[string]any)
+		switch stringFromAny(ent["tp"]) {
+		case "IM":
+			return "image"
+		case "VD":
+			return "video"
+		case "AU":
+			return "voice"
+		case "EX":
+			if file == "" {
+				file = draftyAttachmentType(data)
+			}
+		case "LN":
+			if link == "" {
+				link = "link"
+			}
+		}
+	}
+	if file != "" {
+		return file
+	}
+	return link
+}
+
+func draftyAttachmentType(data map[string]any) string {
+	mime := ""
+	if data != nil {
+		mime = stringFromAny(data["mime"])
+	}
+	switch {
+	case strings.HasPrefix(mime, "image/"):
+		return "image"
+	case strings.HasPrefix(mime, "video/"):
+		return "video"
+	case strings.HasPrefix(mime, "audio/"):
+		return "voice"
+	default:
+		return "file"
+	}
+}
+
 func favoriteSnapshot(msg *types.Message) map[string]any {
 	if msg == nil {
 		return map[string]any{}

server/im_http_test.go

@@ -8002,3 +8002,110 @@ func ptrTime(t time.Time) *time.Time {
 func ptrString(s string) *string {
 	return &s
 }
+
+func TestIMMessageTypeDraftyEntities(t *testing.T) {
+	cases := []struct {
+		name string
+		msg  *types.Message
+		want string
+	}{
+		{
+			name: "nil message",
+			msg:  nil,
+			want: "text",
+		},
+		{
+			name: "drafty link entity",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "check this https://example.com",
+				"fmt": []any{map[string]any{"at": 10, "len": 19, "key": 0}},
+				"ent": []any{map[string]any{"tp": "LN", "data": map[string]any{"url": "https://example.com"}}},
+			}},
+			want: "link",
+		},
+		{
+			name: "drafty image entity",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "a photo",
+				"fmt": []any{map[string]any{"at": 7, "len": 1, "key": 0}},
+				"ent": []any{map[string]any{"tp": "IM", "data": map[string]any{"mime": "image/png", "name": "pic.png"}}},
+			}},
+			want: "image",
+		},
+		{
+			name: "drafty video entity",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "clip",
+				"ent": []any{map[string]any{"tp": "VD", "data": map[string]any{"mime": "video/mp4"}}},
+			}},
+			want: "video",
+		},
+		{
+			name: "drafty audio entity",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "",
+				"ent": []any{map[string]any{"tp": "AU", "data": map[string]any{"mime": "audio/mp4"}}},
+			}},
+			want: "voice",
+		},
+		{
+			name: "drafty generic file entity",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "doc",
+				"ent": []any{map[string]any{"tp": "EX", "data": map[string]any{"mime": "application/pdf", "name": "a.pdf"}}},
+			}},
+			want: "file",
+		},
+		{
+			name: "drafty image file entity refines by mime",
+			msg: &types.Message{Content: map[string]any{
+				"ent": []any{map[string]any{"tp": "EX", "data": map[string]any{"mime": "image/jpeg"}}},
+			}},
+			want: "image",
+		},
+		{
+			name: "drafty attachment wins over inline link",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "see https://example.com and",
+				"fmt": []any{map[string]any{"at": 4, "len": 18, "key": 1}, map[string]any{"at": 26, "len": 1, "key": 0}},
+				"ent": []any{map[string]any{"tp": "EX", "data": map[string]any{"mime": "application/zip"}}, map[string]any{"tp": "LN", "data": map[string]any{}}},
+			}},
+			want: "file",
+		},
+		{
+			name: "drafty plain text",
+			msg: &types.Message{Content: map[string]any{
+				"txt": "hello",
+			}},
+			want: "text",
+		},
+		{
+			name: "legacy flat file_id content still works",
+			msg: &types.Message{Content: map[string]any{"file_id": "file-1", "mime": "image/png"}},
+			want: "image",
+		},
+		{
+			name: "legacy flat url content still works",
+			msg: &types.Message{Content: map[string]any{"url": "https://example.com"}},
+			want: "link",
+		},
+		{
+			name: "head type takes priority",
+			msg: &types.Message{
+				Head:    types.KVMap{"type": "system_notice"},
+				Content: map[string]any{"ent": []any{map[string]any{"tp": "IM"}}},
+			},
+			want: "system_notice",
+		},
+		{
+			name: "string content",
+			msg:  &types.Message{Content: "plain"},
+			want: "text",
+		},
+	}
+	for _, tc := range cases {
+		if got := imMessageType(tc.msg); got != tc.want {
+			t.Errorf("%s: imMessageType = %q, want %q", tc.name, got, tc.want)
+		}
+	}
+}