Typing "@" + 2+ characters now opens a dropdown of matching users
(reusing the existing people-search endpoint), with arrow-key/Enter/
Tab selection and click-to-select. Consolidated the previously
duplicated MENTION_REGEX (client display vs. server extraction) into
a single export from lib/mentions.ts.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Parse @username in comment content, notify mentioned users (dedup
against recipe-author/parent-author who are already notified via
comment/reply), and render @username as a link to their profile.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Arnaud