test: exclude node_modules from tsnapi package discovery

The API-snapshot suite auto-discovers workspace packages, but depending on
the installed layout (pnpm `shamefullyHoist`) that discovery can walk into
`node_modules` and try to snapshot dependencies like `@babel/runtime`,
crashing on their directory-valued `exports` (`EISDIR`). Skip any discovered
package under `node_modules` so only first-party workspace packages are
snapshotted — fixing the intermittent CI failure.

Built with the help of an agent.

Author: antfubot

tests/exports.test.ts

@@ -5,6 +5,12 @@ import { describePackagesApiSnapshots } from 'tsnapi/vitest'
 describePackagesApiSnapshots({
   cwd: fileURLToPath(new URL('..', import.meta.url)),
   filter(ctx) {
+    // Only snapshot first-party workspace packages. Auto-discovery can walk
+    // into `node_modules` depending on the installed layout (e.g. pnpm's
+    // `shamefullyHoist`), which would try to snapshot dependencies like
+    // `@babel/runtime` and crash on their directory-valued `exports`.
+    if (/[\\/]node_modules[\\/]/.test(ctx.packageRoot))
+      return false
     const pkg = JSON.parse(
       readFileSync(`${ctx.packageRoot}/package.json`, 'utf8'),
     )