feat: add Tailwind setup and branch/PR workflow scaffolding

[rileygramlich]

Summary

• add Tailwind CSS pipeline and global app styles
• import global styles in app entrypoint
• add PR template and documented branch-first workflow
• add

contraction-counter@0.1.0 check
npm run build

contraction-counter@0.1.0 build
tsc -b && vite build

vite v5.4.21 building for production...
transforming...
✓ 1671 modules transformed.
rendering chunks...
computing gzip size...
dist/index.html 0.40 kB │ gzip: 0.27 kB
dist/assets/index-DCaxnBbd.css 20.28 kB │ gzip: 4.70 kB
dist/assets/index-BlTyeHSi.js 154.27 kB │ gzip: 49.42 kB
✓ built in 1.72s quality gate

Validation

• npm run check

Hermes Dev self-review

• reviewed changed files for regressions and scope
• verified no unrelated file changes in branch

Notes

• This PR combines the Tailwind setup work plus lightweight workflow docs/template so future changes stay branch/PR disciplined.

[rileygramlich]

Closing as superseded: this branch is 8 commits behind main, and the Tailwind setup and PR workflow it introduced already exist on main. Branch kept for history.