Add a "Start from a template" gallery to the Automations page so users can
scaffold common scheduled agent runs (PR review digest, issue triage,
dependency checks, flaky-test tracking, release notes, docs freshness,
security audit) instead of writing every automation from scratch. Selecting
a template opens the new-automation editor prefilled with its instructions
and a default schedule, which the user can tweak before saving.
Also adds an isDescribableCron helper so template schedules render as
human-readable labels rather than raw cron in the editor.
Co-authored-by: open-swe[bot] <open-swe@users.noreply.github.com>
