fix (codegen): don't duplicate the primary-key getter for 'without rowid' tables

pkg/schema/index.go

@@ -1,10 +1,19 @@
 package schema
 
+type IndexOrigin string
+
+const (
+	IndexOriginCreateIndex      = IndexOrigin("c")
+	IndexOriginUniqueConstraint = IndexOrigin("u")
+	IndexOriginPrimaryKey       = IndexOrigin("pk")
+)
+
 type Index struct {
 	Name      string `db:"index_name"`
 	TableName string `db:"table_name"`
 	Columns   []string
-	IsUnique  bool `db:"is_unique"`
+	IsUnique  bool        `db:"is_unique"`
+	Origin    IndexOrigin `db:"origin"`
 	// TODO: `where ...` for partial indexes
 	// TODO: identify columns that are expressions
 }