Opt-in param preupdate_auto_intercept (off by default). When enabled the
injected update-page script wraps window.Joomla.submitbutton so clicking
the toolbar Update button first pops the progress modal, runs the
pre-update backup, and re-issues the original update task on success.
- Matches only update.update / update.install (not Find Updates /
Clear Cache, which also start with 'update').
- Reuses the phase-1 overlay + ajax.preupdateAck throttle so the
subsequent server-side onExtensionBeforeUpdate backup is skipped.
- The manual 'Back up now' notice remains a fallback for flows that
don't route through submitbutton (e.g. some com_joomlaupdate paths).
Refs #196
Claude-Session: https://claude.ai/code/session_01WbGBN9VyRK61zczYWcCQ2i
jmiller