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/builder.go

@@ -1,7 +1,7 @@
 package schema
 
 import (
-	"git.fsdpf.net/go/db/v2"
+	"git.fsdpf.net/go/db"
 )
 
 type Builder struct {
@@ -48,6 +48,13 @@ func (this Builder) Rename(from, to string) error {
 	return this.Build(bp)
 }
 
+// 修改表备注
+func (this Builder) ModifyComment(table, comment string) error {
+	bp := NewBlueprint(table)
+	bp.ModifyComment(comment)
+	return this.Build(bp)
+}
+
 // 删除表
 func (this Builder) Drop(table string) error {
 	bp := NewBlueprint(table)