Addresses #638, where a prospective Italian translator asked for clearer
translator onboarding and a way to preview translations in place. The new
guide documents where strings live, the four-file registration path for a
new language, and the Vite HMR dev workflow that already solves the live
preview need. Linked from all three READMEs alongside CONTRIBUTING.md.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Charlie