Joomla matches updates to installed extensions via element+type+client_id.
Packages in #__extensions have client_id=0. Omitting <client> caused
Joomla to default to client_id=1, resulting in extension_id=0 in
#__updates and updates not appearing.
Fix: output <client>0</client> for package types.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>