Fix bd-yvlc: in-memory database deadlock in migrations

- Force single connection for all in-memory databases (including file::memory:)
- Close rows before executing statements in external_ref migration
- Prevents connection pool deadlock with MaxOpenConns(1)
- Fixes test failures in syncbranch_test.go

internal/storage/sqlite/migrations/002_external_ref_column.go

@@ -11,7 +11,6 @@ func MigrateExternalRefColumn(db *sql.DB) error {
 	if err != nil {
 		return fmt.Errorf("failed to check schema: %w", err)
 	}
-	defer func() { _ = rows.Close() }()
 
 	for rows.Next() {
 		var cid int
@@ -20,6 +19,7 @@ func MigrateExternalRefColumn(db *sql.DB) error {
 		var dflt *string
 		err := rows.Scan(&cid, &name, &typ, &notnull, &dflt, &pk)
 		if err != nil {
+			rows.Close()
 			return fmt.Errorf("failed to scan column info: %w", err)
 		}
 		if name == "external_ref" {
@@ -29,9 +29,13 @@ func MigrateExternalRefColumn(db *sql.DB) error {
 	}
 
 	if err := rows.Err(); err != nil {
+		rows.Close()
 		return fmt.Errorf("error reading column info: %w", err)
 	}
 
+	// Close rows before executing any statements to avoid deadlock with MaxOpenConns(1)
+	rows.Close()
+
 	if !columnExists {
 		_, err := db.Exec(`ALTER TABLE issues ADD COLUMN external_ref TEXT`)
 		if err != nil {

internal/storage/sqlite/sqlite.go

@@ -56,11 +56,14 @@ func New(path string) (*SQLiteStorage, error) {
 		return nil, fmt.Errorf("failed to open database: %w", err)
 	}
 
-	// For :memory: databases, force single connection to ensure cache sharing works properly.
-	// SQLite's shared cache mode for in-memory databases only works reliably with one connection.
-	// Without this, different connections in the pool can't see each other's writes (bd-b121).
-	if path == ":memory:" {
+	// For all in-memory databases (including file::memory:), force single connection.
+	// SQLite's in-memory databases are isolated per connection by default.
+	// Without this, different connections in the pool can't see each other's writes (bd-b121, bd-yvlc).
+	isInMemory := path == ":memory:" ||
+		(strings.HasPrefix(path, "file:") && strings.Contains(path, "mode=memory"))
+	if isInMemory {
 		db.SetMaxOpenConns(1)
+		db.SetMaxIdleConns(1)
 	}
 
 	// Test connection