Smoke-test the packed packages in real consumers #43

Part of the core extraction (#35). Smoke-test the packed packages in real consumers, so a packaging mistake fails CI instead of a release.

Scope

• npm run smoke packs both packages and installs the tarballs into a plain Node app, a TypeScript app and an Angular app (browser and server, shell and fragment).
• It checks the tarball contents and that the Angular package depends on the core's version.
• A "Packed packages" CI job.

Done when

• The smoke test passes in CI. No library code changes.