- Split clocks: detector timers/cooldowns run on a MONOTONIC clock (immune to an
NTP step on an RTC-less Pi); wall time is used only for the HMAC X-Timestamp
and Event.occurred_at. Fixes false IMMOBILITY / dropped tracks after a clock jump.
- Heartbeat is time-based (30s, predictable regardless of load) and now carries
temp/throttle/queue_pending/config_version telemetry.
- A dead (no-frame) camera counts as erroring instead of a healthy frame, so a
silent monitoring outage no longer looks green.
- Offline queue: isolate one undecodable row instead of wedging every event behind
it; classify 401 (stale clock) as transient, never a poison-drop.
- New edge/health.py: vcgencmd temp/throttle parsing, None off-Pi (no fake 0).
