feat(writers): stamp RelSpec version in generated headers; preserve DBML column order

- Add pkg/buildinfo with Version/BuildDate (set via ldflags, VCS fallback);
  cmd/relspec now sources version info from it
- Emit "RelSpec <version> (built: <date>)" in generated file headers for
  bun, gorm, drizzle, pgsql (incl. migration), mssql, sqlite writers
- pgsql writer: getSortedColumns now sorts by Sequence then Name so the
  streaming WriteSchema/WriteDatabase path preserves source column order
- dbml reader: mergeTable re-bases merged-in column Sequence values past the
  existing max, fixing colliding sequences (and alphabetical fallback) when a
  table is split across multiple DBML files
- Tests for bun/gorm header + column order, and dbml multi-file merge ordering

pkg/writers/bun/template_data.go

@@ -6,6 +6,7 @@ import (
 	"sort"
 	"strings"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -13,6 +14,7 @@ import (
 // TemplateData represents the data passed to the template for code generation
 type TemplateData struct {
 	PackageName string
+	GeneratedBy string
 	Imports     []string
 	Models      []*ModelData
 	Config      *MethodConfig
@@ -165,6 +167,7 @@ func NewTemplateData(packageName string, config *MethodConfig) *TemplateData {
 
 	return &TemplateData{
 		PackageName: packageName,
+		GeneratedBy: buildinfo.GeneratedComment(),
 		Imports:     make([]string, 0),
 		Models:      make([]*ModelData, 0),
 		Config:      config,

pkg/writers/bun/templates.go

@@ -7,7 +7,8 @@ import (
 
 // modelTemplate defines the template for generating Bun models
 const modelTemplate = `// Code generated by relspecgo. DO NOT EDIT.
-package {{.PackageName}}
+{{if .GeneratedBy}}// {{.GeneratedBy}}
+{{end}}package {{.PackageName}}
 
 {{if .Imports -}}
 import (

pkg/writers/bun/writer_test.go

@@ -8,6 +8,7 @@ import (
 	"strings"
 	"testing"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -120,6 +121,42 @@ func TestWriter_WriteTable_MultilineDescriptionProducesValidGo(t *testing.T) {
 	}
 }
 
+func TestWriter_WriteTable_EmbedsRelspecVersionHeader(t *testing.T) {
+	table := models.InitTable("users", "public")
+	table.Columns["id"] = &models.Column{Name: "id", Type: "bigint", IsPrimaryKey: true, NotNull: true, Sequence: 1}
+
+	outputPath := filepath.Join(t.TempDir(), "users.go")
+	writer := NewWriter(&writers.WriterOptions{OutputPath: outputPath, PackageName: "models"})
+	if err := writer.WriteTable(table); err != nil {
+		t.Fatalf("WriteTable() error = %v", err)
+	}
+
+	generated, err := os.ReadFile(outputPath)
+	if err != nil {
+		t.Fatalf("failed to read generated code: %v", err)
+	}
+	src := string(generated)
+
+	if _, err := parser.ParseFile(token.NewFileSet(), outputPath, generated, parser.AllErrors); err != nil {
+		t.Fatalf("generated code is invalid Go: %v\n%s", err, src)
+	}
+
+	wantHeader := "// " + buildinfo.GeneratedComment()
+	if !strings.Contains(src, wantHeader) {
+		t.Errorf("generated code missing RelSpec version header %q\n%s", wantHeader, src)
+	}
+	// The provenance comment must sit between the "Code generated" marker and the package clause.
+	genIdx := strings.Index(src, "// Code generated by relspecgo. DO NOT EDIT.")
+	hdrIdx := strings.Index(src, wantHeader)
+	pkgIdx := strings.Index(src, "package models")
+	if genIdx < 0 || hdrIdx < 0 || pkgIdx < 0 || !(genIdx < hdrIdx && hdrIdx < pkgIdx) {
+		t.Errorf("RelSpec version header is misplaced (gen=%d hdr=%d pkg=%d)\n%s", genIdx, hdrIdx, pkgIdx, src)
+	}
+	if !strings.Contains(wantHeader, "RelSpec ") || !strings.Contains(wantHeader, "(built: ") {
+		t.Errorf("version header not in expected 'RelSpec <version> (built: <date>)' form: %q", wantHeader)
+	}
+}
+
 func TestWriter_WriteDatabase_MultiFile(t *testing.T) {
 	// Create a database with two tables
 	db := models.InitDatabase("testdb")

pkg/writers/drizzle/template_data.go

@@ -4,14 +4,16 @@ import (
 	"sort"
 	"strings"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 )
 
 // TemplateData represents the data passed to the template for code generation
 type TemplateData struct {
-	Imports []string
-	Enums   []*EnumData
-	Tables  []*TableData
+	GeneratedBy string
+	Imports     []string
+	Enums       []*EnumData
+	Tables      []*TableData
 }
 
 // EnumData represents an enum in the schema
@@ -59,7 +61,8 @@ type IndexData struct {
 // NewTemplateData creates a new TemplateData
 func NewTemplateData() *TemplateData {
 	return &TemplateData{
-		Imports: make([]string, 0),
+		GeneratedBy: buildinfo.GeneratedComment(),
+		Imports:     make([]string, 0),
 		Enums:   make([]*EnumData, 0),
 		Tables:  make([]*TableData, 0),
 	}

pkg/writers/drizzle/templates.go

@@ -7,7 +7,8 @@ import (
 
 // schemaTemplate defines the template for generating Drizzle schemas
 const schemaTemplate = `// Code generated by relspecgo. DO NOT EDIT.
-{{range .Imports}}{{.}}
+{{if .GeneratedBy}}// {{.GeneratedBy}}
+{{end}}{{range .Imports}}{{.}}
 {{end}}
 {{if .Enums}}
 // Enums

pkg/writers/gorm/template_data.go

@@ -4,6 +4,7 @@ import (
 	"sort"
 	"strings"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -11,6 +12,7 @@ import (
 // TemplateData represents the data passed to the template for code generation
 type TemplateData struct {
 	PackageName string
+	GeneratedBy string
 	Imports     []string
 	Models      []*ModelData
 	Config      *MethodConfig
@@ -79,6 +81,7 @@ func NewTemplateData(packageName string, config *MethodConfig) *TemplateData {
 
 	return &TemplateData{
 		PackageName: packageName,
+		GeneratedBy: buildinfo.GeneratedComment(),
 		Imports:     make([]string, 0),
 		Models:      make([]*ModelData, 0),
 		Config:      config,

pkg/writers/gorm/templates.go

@@ -7,7 +7,8 @@ import (
 
 // modelTemplate defines the template for generating GORM models
 const modelTemplate = `// Code generated by relspecgo. DO NOT EDIT.
-package {{.PackageName}}
+{{if .GeneratedBy}}// {{.GeneratedBy}}
+{{end}}package {{.PackageName}}
 
 {{if .Imports -}}
 import (

pkg/writers/gorm/writer_test.go

@@ -112,6 +112,46 @@ func TestWriter_WriteTable_MultilineDescriptionProducesValidGo(t *testing.T) {
 	}
 }
 
+func TestWriter_WriteTable_ColumnOrderFollowsSequence(t *testing.T) {
+	// Column.Sequence carries the source (e.g. DBML) declaration order; the
+	// generated struct fields must follow it, not fall back to alphabetical.
+	table := models.InitTable("widget", "public")
+	table.Columns["zeta"] = &models.Column{Name: "zeta", Type: "varchar", Length: 50, Sequence: 1}
+	table.Columns["alpha"] = &models.Column{Name: "alpha", Type: "bigint", NotNull: true, IsPrimaryKey: true, AutoIncrement: true, Sequence: 2}
+	table.Columns["mid_field"] = &models.Column{Name: "mid_field", Type: "integer", Sequence: 3}
+	table.Columns["beta"] = &models.Column{Name: "beta", Type: "varchar", Length: 100, Sequence: 4}
+
+	outputPath := filepath.Join(t.TempDir(), "widget.go")
+	writer := NewWriter(&writers.WriterOptions{OutputPath: outputPath, PackageName: "models"})
+	if err := writer.WriteTable(table); err != nil {
+		t.Fatalf("WriteTable() error = %v", err)
+	}
+
+	generated, err := os.ReadFile(outputPath)
+	if err != nil {
+		t.Fatalf("failed to read generated code: %v", err)
+	}
+	src := string(generated)
+	if _, err := parser.ParseFile(token.NewFileSet(), outputPath, generated, parser.AllErrors); err != nil {
+		t.Fatalf("generated code is invalid Go: %v\n%s", err, src)
+	}
+
+	positions := make([]int, 0, 4)
+	for _, field := range []string{"Zeta ", "Alpha ", "MidField ", "Beta "} {
+		idx := strings.Index(src, "\t"+field)
+		if idx < 0 {
+			t.Fatalf("field %q missing from generated struct:\n%s", field, src)
+		}
+		positions = append(positions, idx)
+	}
+	for i := 1; i < len(positions); i++ {
+		if positions[i] <= positions[i-1] {
+			t.Errorf("struct fields not in Sequence order (want zeta, alpha, mid_field, beta):\n%s", src)
+			break
+		}
+	}
+}
+
 func TestWriter_WriteDatabase_MultiFile(t *testing.T) {
 	// Create a database with two tables
 	db := models.InitDatabase("testdb")

pkg/writers/mssql/writer.go

@@ -11,6 +11,7 @@ import (
 
 	_ "github.com/microsoft/go-mssqldb" // MSSQL driver
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/mssql"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
@@ -68,7 +69,7 @@ func (w *Writer) WriteDatabase(db *models.Database) error {
 	// Write header comment
 	fmt.Fprintf(w.writer, "-- MSSQL Database Schema\n")
 	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
-	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n\n")
+	fmt.Fprintf(w.writer, "-- Generated by %s\n\n", buildinfo.GeneratedComment())
 
 	// Process each schema in the database
 	for _, schema := range db.Schemas {
@@ -477,7 +478,7 @@ func (w *Writer) executeDatabaseSQL(db *models.Database, connString string) erro
 	statements := []string{}
 	statements = append(statements, "-- MSSQL Database Schema")
 	statements = append(statements, fmt.Sprintf("-- Database: %s", db.Name))
-	statements = append(statements, "-- Generated by RelSpec")
+	statements = append(statements, "-- Generated by "+buildinfo.GeneratedComment())
 
 	for _, schema := range db.Schemas {
 		if err := w.generateSchemaStatements(schema, &statements); err != nil {

pkg/writers/pgsql/migration_writer.go

@@ -7,6 +7,7 @@ import (
 	"sort"
 	"strings"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/pgsql"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
@@ -143,7 +144,7 @@ func (w *MigrationWriter) WriteMigration(model, current *models.Database) error
 
 	// Write header
 	fmt.Fprintf(w.writer, "-- PostgreSQL Migration Script\n")
-	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
+	fmt.Fprintf(w.writer, "-- Generated by %s\n", buildinfo.GeneratedComment())
 	fmt.Fprintf(w.writer, "-- Source: %s -> %s\n", current.Name, model.Name)
 	if w.options.ContinueOnError {
 		fmt.Fprintf(w.writer, "\\set ON_ERROR_STOP off\n")

pkg/writers/pgsql/writer.go

@@ -12,6 +12,7 @@ import (
 	"sync"
 	"time"
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/pgsql"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
@@ -101,7 +102,7 @@ func (w *Writer) WriteDatabase(db *models.Database) error {
 	// Write header comment
 	fmt.Fprintf(w.writer, "-- PostgreSQL Database Schema\n")
 	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
-	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
+	fmt.Fprintf(w.writer, "-- Generated by %s\n", buildinfo.GeneratedComment())
 	if w.options.ContinueOnError {
 		fmt.Fprintf(w.writer, "\\set ON_ERROR_STOP off\n")
 	}
@@ -125,7 +126,7 @@ func (w *Writer) GenerateDatabaseStatements(db *models.Database) ([]string, erro
 	// Add header comment
 	statements = append(statements, "-- PostgreSQL Database Schema")
 	statements = append(statements, fmt.Sprintf("-- Database: %s", db.Name))
-	statements = append(statements, "-- Generated by RelSpec")
+	statements = append(statements, "-- Generated by "+buildinfo.GeneratedComment())
 
 	// Process each schema in the database
 	for _, schema := range db.Schemas {
@@ -555,7 +556,7 @@ func (w *Writer) GenerateAddColumnsForDatabase(db *models.Database) ([]string, e
 
 	statements = append(statements, "-- Add missing columns to existing tables")
 	statements = append(statements, fmt.Sprintf("-- Database: %s", db.Name))
-	statements = append(statements, "-- Generated by RelSpec")
+	statements = append(statements, "-- Generated by "+buildinfo.GeneratedComment())
 
 	for _, schema := range db.Schemas {
 		schemaStatements, err := w.GenerateAddColumnStatements(schema)
@@ -1446,19 +1447,10 @@ func (w *Writer) writeComments(schema *models.Schema) error {
 
 // Helper functions
 
-// getSortedColumns returns columns sorted by name
+// getSortedColumns returns columns sorted by Sequence then Name, preserving the
+// original column order from the source schema for deterministic output.
 func getSortedColumns(columns map[string]*models.Column) []*models.Column {
-	names := make([]string, 0, len(columns))
-	for name := range columns {
-		names = append(names, name)
-	}
-	sort.Strings(names)
-
-	sorted := make([]*models.Column, 0, len(columns))
-	for _, name := range names {
-		sorted = append(sorted, columns[name])
-	}
-	return sorted
+	return sortColumns(columns)
 }
 
 // isIntegerType checks if a column type is an integer type

pkg/writers/sqlite/writer.go

@@ -10,6 +10,7 @@ import (
 
 	_ "modernc.org/sqlite" // SQLite driver
 
+	"git.warky.dev/wdevs/relspecgo/pkg/buildinfo"
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
 	"git.warky.dev/wdevs/relspecgo/pkg/writers"
 )
@@ -72,7 +73,7 @@ func (w *Writer) writeContent(db *models.Database) error {
 	// Write header comment
 	fmt.Fprintf(w.writer, "-- SQLite Database Schema\n")
 	fmt.Fprintf(w.writer, "-- Database: %s\n", db.Name)
-	fmt.Fprintf(w.writer, "-- Generated by RelSpec\n")
+	fmt.Fprintf(w.writer, "-- Generated by %s\n", buildinfo.GeneratedComment())
 	fmt.Fprintf(w.writer, "-- Note: SQLite has no schema concept; non-default schema names are flattened into table name prefixes (e.g., auth.sessions -> auth_sessions)\n\n")
 
 	// Enable foreign keys