The cron scheduler tick loop only ran inside `hermes gateway run`, but the
desktop app spawns a `hermes dashboard` backend with no gateway — so any cron
a user created in the app was saved and never fired (silently).
Run a minimal scheduler ticker inside the dashboard lifespan, gated on a new
HERMES_DESKTOP=1 marker the electron shell injects, so server `hermes dashboard`
is unaffected. Cross-process safe via the existing cron/.tick.lock, so it never
double-fires alongside a real gateway.
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