CI deployment pipelines fixed on Linux runners

The CI deployment pipelines had stopped working. Two GitHub Actions workflows — the Vercel deploy action and the GitHub Pages publish action — were failing with "sh: gitpulse: not found" on ubuntu-latest runners. A previous fix attempt using npx --package= worked on macOS but hit an environment-specific quirk on Linux: when a scoped package's bin name doesn't match the package name, npm execs via sh -c against a PATH that doesn't include the temporary install directory.

Deployments are now fixed by switching from npx to npm install -g. The CLI installs to /usr/local/bin/gitpulse and remains on PATH for subsequent steps in the job. The change applies directly to the Vercel deploy workflow and propagates to self-deploy once the next release-please cycle bumps the version forward. All deployment guides in the README have been updated to match. Additionally, .vercel/ workspace state was added to .gitignore to prevent accidentally committing Vercel project IDs.