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/postgres/postgres.go

@@ -3,11 +3,11 @@ package postgres
 import (
 	"strings"
 
-	"git.fsdpf.net/go/db/v2"
-	"git.fsdpf.net/go/db/v2/dialect/postgres"
-	"git.fsdpf.net/go/db/v2/internal/sb"
-	"git.fsdpf.net/go/db/v2/schema"
-	"git.fsdpf.net/go/db/v2/sqlgen"
+	"git.fsdpf.net/go/db"
+	"git.fsdpf.net/go/db/dialect/postgres"
+	"git.fsdpf.net/go/db/internal/sb"
+	"git.fsdpf.net/go/db/schema"
+	"git.fsdpf.net/go/db/sqlgen"
 )
 
 type Postgres struct {
@@ -41,7 +41,7 @@ func (this Postgres) TableExists(table string) (bool, error) {
 
 func (this Postgres) CompileCreate(bp *schema.Blueprint) []string {
 	temporary := db.L("CREATE")
-	if bp.IsTemporary() {
+	if bp.Temporary {
 		temporary = db.L("CREATE TEMPORARY")
 	}
 	columns := strings.Join(this.getAddedColumns(bp), ",\n")
@@ -96,6 +96,11 @@ func (this Postgres) CompileRename(bp *schema.Blueprint) []string {
 	return []string{this.GenerateSQL("ALTER TABLE ? RENAME TO ?", db.T(bp.GetTable()), db.T(toName))}
 }
 
+// 修改表备注
+func (this Postgres) CompileModifyComment(bp *schema.Blueprint) []string {
+	return []string{this.GenerateSQL("COMMENT ON TABLE ? IS ?", db.T(bp.GetTable()), db.V(bp.Comment))}
+}
+
 func (this Postgres) addModifiers(sql string, bp *schema.Blueprint, column *schema.ColumnDefinition) string {
 	for _, modifier := range pgDefaultModifiers {
 		sql += this.GetColumnModifier(modifier, bp, column)