R6(c): centralize shared integration-test fixtures in helpers.go

Move the cross-file integration fixtures — the service constructors
(newGameService/newSocialService/newRobotService/newMatchmaker), the game-assembly
helpers (newMirror/newGameWithSeats/newDraftGame), account provisioning
(provisionAccount/provisionGuest) and the stats reader — out of the domain test
files (newGameService alone was used by 10 files) into a single
backend/internal/inttest/helpers.go. Helpers used by a single file stay local.

Pure relocation: the helper bodies are unchanged, no test logic changes; the
imports the moves left unused are pruned. go vet -tags=integration is clean.

backend/internal/inttest/game_test.go

@@ -4,88 +4,17 @@ package inttest
 
 import (
 	"context"
-	"database/sql"
 	"errors"
 	"sync"
 	"testing"
 	"time"
 
 	"github.com/google/uuid"
-	"go.uber.org/zap"
 
-	"scrabble/backend/internal/account"
 	"scrabble/backend/internal/engine"
 	"scrabble/backend/internal/game"
 )
 
-// newGameService builds a game service over the shared pool and registry.
-func newGameService() *game.Service {
-	return game.NewService(
-		game.NewStore(testDB),
-		account.NewStore(testDB),
-		testRegistry,
-		game.Config{
-			DictDir:              dictDir(),
-			DictVersion:          testDictVersion,
-			TimeoutSweepInterval: time.Minute,
-			CacheTTL:             time.Hour,
-		},
-		zap.NewNop(),
-	)
-}
-
-// provisionAccount creates a fresh durable account and returns its id.
-func provisionAccount(t *testing.T) uuid.UUID {
-	t.Helper()
-	acc, err := account.NewStore(testDB).ProvisionByIdentity(context.Background(), account.KindTelegram, "tg-"+uuid.NewString())
-	if err != nil {
-		t.Fatalf("provision account: %v", err)
-	}
-	return acc.ID
-}
-
-// openingSeed returns a seed whose fresh two-player English opening rack has a
-// legal move, so a greedy mirror can drive a game.
-func openingSeed(t *testing.T) int64 {
-	t.Helper()
-	for seed := int64(1); seed <= 200; seed++ {
-		g, err := engine.New(testRegistry, engine.Options{Variant: engine.VariantEnglish, Version: testDictVersion, Players: 2, Seed: seed})
-		if err != nil {
-			t.Fatalf("engine new: %v", err)
-		}
-		if _, ok := g.HintView(); ok {
-			return seed
-		}
-	}
-	t.Fatal("no opening seed found")
-	return 0
-}
-
-// newMirror builds a parallel engine game with the same seed, used to compute
-// legal moves to feed the service under test.
-func newMirror(t *testing.T, seed int64, players int) *engine.Game {
-	t.Helper()
-	g, err := engine.New(testRegistry, engine.Options{Variant: engine.VariantEnglish, Version: testDictVersion, Players: players, Seed: seed})
-	if err != nil {
-		t.Fatalf("mirror new: %v", err)
-	}
-	return g
-}
-
-// readStats reads an account's statistics row.
-func readStats(t *testing.T, id uuid.UUID) (wins, losses, draws, maxGame, maxWord int, found bool) {
-	t.Helper()
-	row := testDB.QueryRowContext(context.Background(),
-		`SELECT wins, losses, draws, max_game_points, max_word_points FROM backend.account_stats WHERE account_id = $1`, id)
-	if err := row.Scan(&wins, &losses, &draws, &maxGame, &maxWord); err != nil {
-		if errors.Is(err, sql.ErrNoRows) {
-			return 0, 0, 0, 0, 0, false
-		}
-		t.Fatalf("read stats: %v", err)
-	}
-	return wins, losses, draws, maxGame, maxWord, true
-}
-
 // TestListForAccount checks the lobby "my games" query: it returns exactly the
 // games the account is seated in (each with its seats), and nothing for an outsider.
 func TestListForAccount(t *testing.T) {