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>

exec/scanner_internal_test.go

@@ -3,6 +3,7 @@ package exec
 import (
 	"testing"
 
+	"git.fsdpf.net/go/db/exp"
 	"github.com/DATA-DOG/go-sqlmock"
 	"github.com/stretchr/testify/suite"
 )
@@ -67,3 +68,27 @@ func (s *scannerSuite) TestScanVals() {
 	s.Require().NoError(err)
 	s.Require().ElementsMatch([]int{1, 2}, result)
 }
+
+func (s *scannerSuite) TestGetRecords() {
+	db, mock, err := sqlmock.New()
+	s.Require().NoError(err)
+
+	mock.ExpectQuery("SELECT \\* FROM `items`").
+		WithArgs().
+		WillReturnRows(
+			sqlmock.NewRows([]string{"address", "name"}).
+				AddRow("111 Test Addr", "Test1").
+				AddRow("111 Test Addr", "Test1"),
+		)
+
+	rows, err := db.Query("SELECT \\* FROM `items`")
+	s.Require().NoError(err)
+
+	result, err := NewScanner(rows).GetRecords()
+	s.Require().NoError(err)
+
+	s.Equal([]exp.Record{
+		{"address": "111 Test Addr", "name": "Test1"},
+		{"address": "111 Test Addr", "name": "Test1"},
+	}, result)
+}