feat(accountdelete): drop all-robot games + unspoofable [Deleted] label

Q2=B: DropAllRobotGames deletes the deletee's games with no human opponent (vs-AI or
auto-match-robot; children cascade), keeping games with any human seat (anonymized
instead). Q1=A: the anon label is the sentinel [Deleted] — the editable-name rule forbids
brackets, so no live player can impersonate a deleted account. Integration test covers
drop-vs-keep.

backend/internal/inttest/delete_test.go

@@ -12,6 +12,8 @@ import (
 
 	"scrabble/backend/internal/account"
 	"scrabble/backend/internal/accountdelete"
+	"scrabble/backend/internal/engine"
+	"scrabble/backend/internal/game"
 )
 
 // deletedFields reads a tombstoned account's retained real name and its deleted_at.
@@ -90,3 +92,44 @@ func TestAnonymizeAndTombstone(t *testing.T) {
 		t.Fatalf("email should be free after deletion, got: %v", err)
 	}
 }
+
+// TestDropAllRobotGames drops the deletee's solo vs-AI game but keeps a game with a human
+// opponent.
+func TestDropAllRobotGames(t *testing.T) {
+	ctx := context.Background()
+	gsvc := newGameService()
+	robots := newRobotService(t, gsvc)
+	if err := robots.EnsurePool(ctx); err != nil {
+		t.Fatalf("ensure pool: %v", err)
+	}
+	mm := newMatchmaker(t, robots, time.Minute, 0)
+	deleter := accountdelete.NewDeleter(testDB)
+
+	user := provisionAccount(t)
+	other := provisionAccount(t)
+
+	aiRes, err := mm.StartVsAI(ctx, user, engine.VariantEnglish, true)
+	if err != nil {
+		t.Fatalf("start vs AI: %v", err)
+	}
+	humanGame, err := gsvc.Create(ctx, game.CreateParams{
+		Variant: engine.VariantEnglish, Seats: []uuid.UUID{user, other}, TurnTimeout: time.Hour, Seed: 1,
+	})
+	if err != nil {
+		t.Fatalf("create human game: %v", err)
+	}
+
+	n, err := deleter.DropAllRobotGames(ctx, user)
+	if err != nil {
+		t.Fatalf("drop: %v", err)
+	}
+	if n != 1 {
+		t.Fatalf("dropped %d games, want 1 (the vs-AI game)", n)
+	}
+	if _, err := gsvc.GameByID(ctx, aiRes.Game.ID); err == nil {
+		t.Error("the vs-AI game should be dropped")
+	}
+	if _, err := gsvc.GameByID(ctx, humanGame.ID); err != nil {
+		t.Errorf("the human game should be kept, got: %v", err)
+	}
+}