build: two-step for packages/vendor build and README

vendor/schemastery/tsdown.config.ts

@@ -2,12 +2,12 @@ import { defineConfig } from 'tsdown'
 
 /**
  * schemastery has no `"type": "module"` and publishes dual-format output
- * (package.json: main → lib/index.cjs, module → lib/index.mjs). Pin the
- * extensions explicitly — the defaults for a CommonJS package would emit
- * .mjs/.js instead.
+ * (package.json: main → lib/index.cjs, module → lib/index.mjs). The entry is
+ * the JS emitted by tsc under lib/typings; pin the bundled extensions
+ * explicitly because the defaults for a CommonJS package would emit .mjs/.js.
  */
 export default defineConfig({
-  entry: ['src/index.ts'],
+  entry: ['lib/typings/index.js'],
   outDir: 'lib',
   format: ['esm', 'cjs'],
   platform: 'node',