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/readers/gorm/reader.go

@@ -726,6 +726,15 @@ func (r *Reader) parseColumn(fieldName string, fieldType ast.Expr, tag string, s
 	if _, ok := parts["autoincrement"]; ok {
 		column.AutoIncrement = true
 	}
+	if _, ok := parts["generated"]; ok {
+		// GENERATED ... STORED marker written by the GORM writer; the expression is not in the tag
+		column.Generated = true
+	}
+	if _, ok := parts["identity"]; ok {
+		// GENERATED ALWAYS AS IDENTITY marker written by the GORM writer
+		column.Identity = true
+		column.IdentityGeneration = "ALWAYS"
+	}
 	if def, ok := parts["default"]; ok {
 		// Default value from GORM tag (e.g., default:gen_random_uuid())
 		column.Default = def