Restore NPM_TOKEN to publish workflow (OpenRouterTeam#228)

- Add NPM_TOKEN back to changesets action environment
- Remove .npmrc experiment (didn't work)
- NPM_TOKEN needed for authentication, --provenance uses OIDC for attestations
- Token may be configured at organization level

Author: subtleGradient

.github/workflows/publish.yaml

@@ -36,3 +36,4 @@ jobs:
           publish: pnpm changeset-publish
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          NPM_TOKEN: ${{ secrets.NPM_TOKEN }}