The #115692 reclaim released any running attempt whose claim was older than
max(3 x HERMES_CRON_TIMEOUT, script timeout, 2 h), even when the owner was
healthy and busy. Every cron job that legitimately ran longer than that was
marked `unknown` mid-run, its fire claim yanked from under it and the run
aborted with "lost its durable fire claim ownership" (two weekly jobs on one
install in a single day).
The run monitor now stamps `progress_at` on the execution row every 60 s
while the agent reports recent activity, and the sweep measures the stale
bound from that stamp (claim age for legacy rows). A wedged worker stops
stamping and is still reclaimed once the bound passes.
Shape: the stamper and the inactivity watchdog loop (which reads the same
idle signal) live in a new topical sibling cron/scheduler_liveness.py, so
cron/scheduler.py shrinks (4457 -> 4436 lines) instead of growing.
ed2dd0b35c