Stage 17 round 6 (#16/#17, PR C): lobby sort + server-derived in-game friend state

Lobby: group the my-games list into your-turn / opponent-turn / finished
(empty sections hidden), ordered by last activity (your-turn oldest-first,
the other two newest-first), as a compact line-separated list. gameDTO and
FB GameView gain last_activity_unix (turn start while active, finish time
once finished); a pure lib/lobbysort.ts holds the grouping/ordering.

Friends: the in-game 'add to friends' item is now server-derived via a new
GET /user/friends/outgoing (+ friends.outgoing op), returning addressees with
a pending OR declined request (both read as 'request sent'), so it is correct
across reloads; it shows a disabled '✓ in friends' once accepted. It
live-updates when the opponent answers: RespondFriendRequest now publishes
friend_added (accept) / friend_declined (new notify sub-kind, decline) to the
original requester, whose open game re-derives its friend state.

Tests: lobbysort unit test; gateway outgoing + last_activity transcode tests;
backend integration ListOutgoingRequests + respond-publishes-to-requester;
e2e updated for the new lobby section labels + a non-friend active opponent.
Docs: ARCHITECTURE notify catalog, FUNCTIONAL(+ru) lobby/friends, PLAN.

gateway/internal/transcode/encode.go

@@ -357,6 +357,7 @@ func buildGameView(b *flatbuffers.Builder, g backendclient.GameResp) flatbuffers
 	fb.GameViewAddMoveCount(b, int32(g.MoveCount))
 	fb.GameViewAddEndReason(b, endReason)
 	fb.GameViewAddSeats(b, seats)
+	fb.GameViewAddLastActivityUnix(b, g.LastActivityUnix)
 	return fb.GameViewEnd(b)
 }
 

gateway/internal/transcode/encode_social.go

@@ -54,6 +54,16 @@ func encodeIncomingList(r backendclient.IncomingListResp) []byte {
 	return b.FinishedBytes()
 }
 
+// encodeOutgoingList builds an OutgoingRequestList payload.
+func encodeOutgoingList(r backendclient.OutgoingListResp) []byte {
+	b := flatbuffers.NewBuilder(256)
+	v := buildAccountRefVector(b, r.Requests, fb.OutgoingRequestListStartRequestsVector)
+	fb.OutgoingRequestListStart(b)
+	fb.OutgoingRequestListAddRequests(b, v)
+	b.Finish(fb.OutgoingRequestListEnd(b))
+	return b.FinishedBytes()
+}
+
 // encodeBlockList builds a BlockList payload.
 func encodeBlockList(r backendclient.BlockListResp) []byte {
 	b := flatbuffers.NewBuilder(256)

gateway/internal/transcode/transcode_social.go

@@ -13,6 +13,7 @@ import (
 const (
 	MsgFriendsList       = "friends.list"
 	MsgFriendsIncoming   = "friends.incoming"
+	MsgFriendsOutgoing   = "friends.outgoing"
 	MsgFriendRequest     = "friends.request"
 	MsgFriendRespond     = "friends.respond"
 	MsgFriendCancel      = "friends.cancel"
@@ -37,6 +38,7 @@ const (
 func registerStage8(r *Registry, backend *backendclient.Client) {
 	r.ops[MsgFriendsList] = Op{Handler: friendsListHandler(backend), Auth: true}
 	r.ops[MsgFriendsIncoming] = Op{Handler: friendsIncomingHandler(backend), Auth: true}
+	r.ops[MsgFriendsOutgoing] = Op{Handler: friendsOutgoingHandler(backend), Auth: true}
 	r.ops[MsgFriendRequest] = Op{Handler: friendRequestHandler(backend), Auth: true}
 	r.ops[MsgFriendRespond] = Op{Handler: friendRespondHandler(backend), Auth: true}
 	r.ops[MsgFriendCancel] = Op{Handler: friendCancelHandler(backend), Auth: true}
@@ -78,6 +80,16 @@ func friendsIncomingHandler(backend *backendclient.Client) Handler {
 	}
 }
 
+func friendsOutgoingHandler(backend *backendclient.Client) Handler {
+	return func(ctx context.Context, req Request) ([]byte, error) {
+		res, err := backend.ListOutgoing(ctx, req.UserID)
+		if err != nil {
+			return nil, err
+		}
+		return encodeOutgoingList(res), nil
+	}
+}
+
 func friendRequestHandler(backend *backendclient.Client) Handler {
 	return func(ctx context.Context, req Request) ([]byte, error) {
 		in := fb.GetRootAsTargetRequest(req.Payload, 0)

gateway/internal/transcode/transcode_social_test.go

@@ -54,6 +54,35 @@ func TestFriendsListRoundTripDecodesNames(t *testing.T) {
 	}
 }
 
+func TestFriendsOutgoingRoundTrip(t *testing.T) {
+	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/v1/user/friends/outgoing" {
+			t.Errorf("unexpected path %q", r.URL.Path)
+		}
+		_, _ = w.Write([]byte(`{"requests":[{"account_id":"o-1","display_name":"Pat"}]}`))
+	})
+	defer cleanup()
+
+	reg := transcode.NewRegistry(backend, nil)
+	op, ok := reg.Lookup(transcode.MsgFriendsOutgoing)
+	if !ok {
+		t.Fatal("friends.outgoing not registered")
+	}
+	payload, err := op.Handler(context.Background(), transcode.Request{UserID: "u-1"})
+	if err != nil {
+		t.Fatalf("handler: %v", err)
+	}
+	ol := fb.GetRootAsOutgoingRequestList(payload, 0)
+	if ol.RequestsLength() != 1 {
+		t.Fatalf("outgoing length = %d, want 1", ol.RequestsLength())
+	}
+	var ref fb.AccountRef
+	ol.Requests(&ref, 0)
+	if string(ref.AccountId()) != "o-1" || string(ref.DisplayName()) != "Pat" {
+		t.Fatalf("outgoing[0] = (%q, %q), want (o-1, Pat)", ref.AccountId(), ref.DisplayName())
+	}
+}
+
 func TestFriendRequestForwardsTarget(t *testing.T) {
 	backend, cleanup := fakeBackend(t, func(w http.ResponseWriter, r *http.Request) {
 		if got := r.Header.Get("X-User-ID"); got != "u-1" {

gateway/internal/transcode/transcode_test.go

@@ -158,7 +158,7 @@ func TestGamesListRoundTripDecodesSeatNames(t *testing.T) {
 		if r.URL.Path != "/api/v1/user/games" {
 			t.Errorf("unexpected path %q", r.URL.Path)
 		}
-		_, _ = w.Write([]byte(`{"games":[{"id":"g-1","variant":"english","status":"active","players":2,"to_move":0,"seats":[{"seat":0,"account_id":"u-9","display_name":"You","score":10},{"seat":1,"account_id":"a-1","display_name":"Ann","score":7}]}]}`))
+		_, _ = w.Write([]byte(`{"games":[{"id":"g-1","variant":"english","status":"active","players":2,"to_move":0,"last_activity_unix":1717000000,"seats":[{"seat":0,"account_id":"u-9","display_name":"You","score":10},{"seat":1,"account_id":"a-1","display_name":"Ann","score":7}]}]}`))
 	})
 	defer cleanup()
 
@@ -177,6 +177,9 @@ func TestGamesListRoundTripDecodesSeatNames(t *testing.T) {
 	if string(g.Id()) != "g-1" {
 		t.Errorf("game id = %q, want g-1", g.Id())
 	}
+	if g.LastActivityUnix() != 1717000000 {
+		t.Errorf("last activity = %d, want 1717000000", g.LastActivityUnix())
+	}
 	var seat fb.SeatView
 	g.Seats(&seat, 1)
 	if string(seat.DisplayName()) != "Ann" {