hive-c0re: reconcile declared agents periodically, with backoff

docs/4-implementation/scheduler/coordinator.md

@@ -321,6 +321,31 @@ operator sees at a glance how much work the boot triggered. `auto_update::run`
 seeds agents without an intent from observed state during classification, so a
 boot with no operator action in this process never finds drift of its own.
 
+### Periodic reconcile tick
+
+Once a minute (first tick one minute after boot), `workers::reconcile_tick`
+looks for an agent that the hive wants up and whose container is down. It reads
+the power intent, the container's unit state, the pause marker and
+`Coordinator::is_updating`, then queues the same `Reconcile` node the boot power
+path uses, through `JobQueue::insert_reconcile_if_idle`. The tick never stops
+anything.
+
+It leaves an agent alone when:
+
+- its intent is unknown or `Offline`, or its container runs;
+- the agent has its pause marker, an update in progress, or a container state
+  the tick can't read in time;
+- any queued or running node targets it (update, create, destroy, power op or
+  an earlier reconcile). The busy check and the insert share one lock.
+
+An agent still down on the tick after the tick queued a restart has failed to
+come up, so the tick spaces restarts of one agent 1, 2, 4, 8, then 15 ticks
+apart (a 15-minute cap). Seeing the agent running, or no longer wanted up,
+resets the spacing. Each restart logs `reconcile tick: restarting agent` with
+the agent, `observed=stopped`, `wanted=up` and the attempt number, and bumps
+`hyperhive.hive.reconcile_tick.restarts`. `crash_watch` keeps raising its
+alert; the tick only converges.
+
 ## Meta flake
 
 Agents build from the swarm's `internal/meta` flake, which swarm-controller