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>

exp/delete_clauses_test.go

@@ -3,7 +3,7 @@ package exp_test
 import (
 	"testing"
 
-	"git.fsdpf.net/go/db/v2/exp"
+	"git.fsdpf.net/go/db/exp"
 	"github.com/stretchr/testify/suite"
 )
 
@@ -17,7 +17,7 @@ func TestDeleteClausesSuite(t *testing.T) {
 
 func (dcs *deleteClausesSuite) TestHasFrom() {
 	c := exp.NewDeleteClauses()
-	c2 := c.SetFrom(exp.NewIdentifierExpression("", "test", ""))
+	c2 := c.SetFrom(exp.NewColumnListExpression("test"))
 
 	dcs.False(c.HasFrom())
 
@@ -26,7 +26,7 @@ func (dcs *deleteClausesSuite) TestHasFrom() {
 
 func (dcs *deleteClausesSuite) TestFrom() {
 	c := exp.NewDeleteClauses()
-	ti := exp.NewIdentifierExpression("", "a", "")
+	ti := exp.NewColumnListExpression("a")
 	c2 := c.SetFrom(ti)
 
 	dcs.Nil(c.From())
@@ -36,7 +36,7 @@ func (dcs *deleteClausesSuite) TestFrom() {
 
 func (dcs *deleteClausesSuite) TestSetFrom() {
 	c := exp.NewDeleteClauses()
-	ti := exp.NewIdentifierExpression("", "a", "")
+	ti := exp.NewColumnListExpression("a")
 	c2 := c.SetFrom(ti)
 
 	dcs.Nil(c.From())