The daemon's periodic update check now installs a newer release instead
of only refreshing the hint cache: it reuses the update.rs install path
(download, sha256 verify, extract, replace), skips the round while any
agent session is live, and otherwise restarts itself into the new binary
(spawns a detached replacement that waits for the old pid, then exits).
On by default; BSK_AUTO_UPDATE=off keeps the old cache/hint-only
behaviour. Windows can only stage the replacement, so it just logs that
a restart is needed. The CLI hint wording reflects the switch.
* fix(update): run periodic update check in daemon so hints actually fire
The CLI spawned a detached thread to refresh ~/.bsk/update-check.json,
but the process exits as soon as the command finishes, killing the
thread before the fetch could complete — so the cache was never
written and the new-version hint never showed.
Move the periodic check into the daemon: a tokio task ticks every
30 minutes (down from 24h), refreshes the cache when missing/stale,
and logs failures at warn/info into the daemon log. The CLI path is
now read-only: it prints the hint only from a fresh cache and never
spawns threads or touches the network.
* fix(update): decouple daemon refresh window so checks truly run every 30min
The refresh decision reused the 30min tick interval as its freshness
window, and with is_fresh()'s inclusive bound a cache written just
after tick N still counted as fresh at tick N+1 — so in steady state
the daemon only refetched every other tick (~60min).
Judge staleness against DAEMON_REFRESH_WINDOW (25min = 5/6 of the
tick) instead: every 30min tick now finds the cache stale and really
refreshes, while a daemon restarted with a younger-than-25min cache
still skips its first tick. CLI hint freshness semantics
(UPDATE_CHECK_INTERVAL = 30min) are unchanged.
