Timer drop-ins for bare-cron (see packages/bare-os-booter/lib/bare-cron.js).

Install files named `*.timer` under:

  $HOME/.config/bare-os/timers/

(max 8 timer files). See `every-ms.timer.example` and `on-calendar.timer.example` in this directory — copy and rename to `something.timer`.

Clock semantics: `OnCalendar=` / crontab fields use the host wall clock. `every-ms=` timers
default to `setInterval` (drift vs wall is possible). Set `BARE_OS_TIMER_EVERY_MS_MONOTONIC=1`
in the guest environment to chain `setTimeout` callbacks so each firing waits a full period
after the previous job finishes (monotonic cadence, not wall-aligned).