fix: avoid ESM lexer imports in migration bundles

packages/custom-widgets/src/core/scoped-styles.ts

@@ -1,4 +1,13 @@
-import { generate, ident, parse, walk } from "css-tree";
+// Consumers compile this source directly and need the modular export declarations.
+// oxlint-disable-next-line typescript/triple-slash-reference
+/// <reference path="../css-tree.d.ts" />
+
+import generate from "css-tree/generator";
+import parse from "css-tree/parser";
+import { ident } from "css-tree/utils";
+import walk from "css-tree/walker";
+
+// The full entrypoint loads lexer data through import.meta.url, which cannot run in bundled CJS migrations.
 
 const allowedAtRules = new Set(["media", "supports", "container", "keyframes", "-webkit-keyframes"]);
 const animationKeywords = new Set([

packages/custom-widgets/src/css-tree.d.ts

@@ -0,0 +1,19 @@
+// css-tree's modular exports use the same APIs as its typed root entrypoint.
+declare module "css-tree/generator" {
+  import { generate } from "css-tree";
+  export default generate;
+}
+
+declare module "css-tree/parser" {
+  import { parse } from "css-tree";
+  export default parse;
+}
+
+declare module "css-tree/utils" {
+  export { ident } from "css-tree";
+}
+
+declare module "css-tree/walker" {
+  import { walk } from "css-tree";
+  export default walk;
+}