feat: generated and identity columns for mssql, sqlite, drizzle, typeorm, bun and gorm readers

- mssql: write computed columns (AS (expr) PERSISTED) and identity; read computed definition and identity
- sqlite: write GENERATED ALWAYS AS (expr) STORED; read generated columns via table_xinfo and parse the expression
- drizzle: generatedAlwaysAs / generated(Always|ByDefault)AsIdentity, read and write
- typeorm: asExpression/generatedType and identity decorators, read and write; decorator scan is now quote-aware
- bun, gorm readers: read generated and identity markers
- readmes updated

pkg/writers/mssql/writer.go

@@ -187,6 +187,16 @@ func (w *Writer) writeCreateTable(schema *models.Schema, table *models.Table) er
 func (w *Writer) generateColumnDefinition(col *models.Column) string {
 	parts := []string{fmt.Sprintf("[%s]", col.Name)}
 
+	// Computed column: "name AS (expr) PERSISTED" has no data type and cannot carry
+	// IDENTITY or a DEFAULT. PERSISTED mirrors the stored semantics of Column.Generated.
+	if col.Generated && col.GenerationExpression != "" {
+		parts = append(parts, fmt.Sprintf("AS (%s) PERSISTED", col.GenerationExpression))
+		if col.NotNull {
+			parts = append(parts, "NOT NULL")
+		}
+		return strings.Join(parts, " ")
+	}
+
 	// Type with length/precision
 	baseType := mssql.ConvertCanonicalToMSSQL(col.Type)
 	typeStr := baseType
@@ -215,7 +225,7 @@ func (w *Writer) generateColumnDefinition(col *models.Column) string {
 	parts = append(parts, typeStr)
 
 	// IDENTITY for auto-increment
-	if col.AutoIncrement {
+	if col.AutoIncrement || col.Identity {
 		parts = append(parts, "IDENTITY(1,1)")
 	}