docs: Add CLAUDE.md with codebase guidance

Create comprehensive documentation for future Claude Code instances working in this repository, including:
- Development commands for testing, building, and code quality
- Core architecture overview of the SQL query builder system
- Directory structure and component explanations
- Testing patterns and conventions
- Key dependencies and their purposes

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

schema/dialect/mysql/mysql_test.go

@@ -4,9 +4,9 @@ import (
 	"os"
 	"testing"
 
-	"git.fsdpf.net/go/db/v2"
-	"git.fsdpf.net/go/db/v2/engine"
-	"git.fsdpf.net/go/db/v2/schema"
+	"git.fsdpf.net/go/db"
+	"git.fsdpf.net/go/db/engine"
+	"git.fsdpf.net/go/db/schema"
 	"github.com/stretchr/testify/suite"
 
 	_ "github.com/go-sql-driver/mysql"
@@ -71,7 +71,7 @@ func (t *mysqlTest) TestTableExists() {
 func (t *mysqlTest) TestCompileCreate() {
 	bp := schema.NewBlueprint("users")
 	bp.Create()
-	bp.Charset("utf8mb4")
+	bp.Charset = "utf8mb4"
 
 	bp.BigIncrements("id").AutoIncrement().Comment("ID")
 	bp.Boolean("enabled").Default("1").Comment("是否有效")
@@ -188,3 +188,5 @@ func (t *mysqlTest) TestCompileRename() {
 
 	t.T().Log(sql)
 }
+
+// 修改表备注