codegen (refactor): clean up helpers a bit

pkg/codegen/modelgenerate/ast_helpers.go

@@ -0,0 +1,11 @@
+package modelgenerate
+
+import "go/ast"
+
+// mustCall wraps a call expression in Must(...), producing AST for Must(inner).
+func mustCall(inner ast.Expr) *ast.CallExpr {
+	return &ast.CallExpr{
+		Fun:  ast.NewIdent("Must"),
+		Args: []ast.Expr{inner},
+	}
+}