Revert component-library release publish path to npm for main-build

[Copilot]

main-build in the Component Library release workflow started failing at publish time, while build steps still succeeded. The failure was isolated to the recent switch from npm publish to pnpm publish.

• Release workflow: restore known-good publish path

  • Reintroduced npm upgrade step used by prior successful releases.
  • Replaced pnpm publish --no-git-checks --provenance with npm publish --tag ${{ env.RELEASE_CHANNEL }}.

• Scope

  • Only .github/workflows/design-library-release.yml was changed.
  • No package/runtime code changes.

- run: |
    npm install -g npm@~11.10.0
    npm install -g npm@latest # Required for trusted publishing (npm 11.5.1 or later)

- name: Publish `@bcc-code/component-library-vue`
  run: npm publish --tag ${{ env.RELEASE_CHANNEL }}