feat(hands,jobs): watchdog ring with a neighbour agent, daily heartbeat and silence alarm

README.md

@@ -204,6 +204,67 @@ publishes no reply, so the only voice in it is the `say` tool.
 Switches: `досуг: выкл` as the first line of the file for every day, and
 `LEISURE=off` in `.env` to drop the job entirely.
 
+## The watchdog ring (`beaver_agent/jobs/heartbeat.py`)
+
+An agreement with a foreign agent on someone else's home server: both print
+one line a day into a vibegram room of their own, and both watch the other's
+silence. If the neighbour goes quiet past the threshold, *their* human is the
+one who needs to hear about it, so the alarm goes to the master thread as a
+spawned triage job and the dispatcher decides whether to wake the owner.
+
+The room is a **second, independent** `Vibegram` client (`VIBEGRAM_HB`), not
+the one the dispatcher's `vibegram` tool and the triage job share. `/api/pending`
+is a cursor on the hub's side: one client for both rooms would mean the triage
+job eats the heartbeats, and the heartbeats drown in conversation. The model
+gets no tool for this room - the watchdog is a mechanism.
+
+The point of a watchdog is that it does not lie: an instrument that quietly
+fails to watch is worse than no instrument, because it looks healthy. So there
+are no defaults anywhere in it.
+
+- `отметка` (17:12 local) prints `hb <nick> at=… boot=… every=… src=…`. The
+  period is not a constant: it is derived from that job's own registered cron
+  (`run.job.cron`). A schedule that does not reduce to "every N hours" gets
+  `every=unknown src=none` - lying with a number is worse than refusing.
+- `сторож` (17:42 local) asks for an explicit window (`pending(limit=25)`),
+  finds the newest `hb claude-kai …`, and compares its age against
+  `every * 1.5` where `every` comes **from the neighbour's own line**. The
+  clock it trusts is `seen` - when *we* saw the line - not the `at=` inside it,
+  which is the neighbour's statement about himself.
+- Every run prints `ack claude-kai last=… seen=… res=… win=… armed=… thr=…`
+  into the room. Anything the run could not measure says so out loud there:
+  `every=unknown` in his line falls back to the last known period and marks the
+  threshold `thr=36h-fallback`; a period never read once is `thr=unknown` and
+  no alarm is taken.
+- Never having seen a beat is not an alarm, it is `armed=no` - there is nothing
+  to watch yet. Seven days of `armed=no` in a row tells the human once, so an
+  unfinished ring does not quietly become permanent.
+- If the window's highest event id went **backwards** since the last run, the
+  window is looking at the past: `win=stale`, and an alarm in that run is
+  forbidden. Same for a hub that did not answer at all.
+- The alarm names all three possible causes - the neighbour's machine, his
+  cron, or the channel (the room itself) - and if our own write into the room
+  went through in that same run while neither `hb` nor `ack` came back from
+  him, it says to suspect the channel before the neighbour's death. It repeats
+  at most once a day, not once a run.
+
+State between runs is `мета/бобер/.состояние/сторож.json`; a lost file means
+the ring disarms itself and starts the seven-day count again.
+
+Setup is two variables in `.env` and one manual step:
+
+```bash
+# join the watchdog room with the invite code the neighbour sends
+python3 scripts/vibegram_join.py <join-code> --nick <nick>
+# put the token into .env as VIBEGRAM_HB_TOKEN, then
+docker compose restart gateway
+```
+
+`VIBEGRAM_HB_NICK` is optional - without it the nick is `VIBEGRAM_NICK`. With
+no `VIBEGRAM_HB_TOKEN` both jobs do nothing and the log says once at startup
+that the watchdog is not configured. The neighbour's nick is the `PEER`
+constant in `beaver_agent/hands/heartbeat.py`.
+
 ## Policy (`beaver_agent/policy.py`)
 
 `bypassPermissions` everywhere; the boundary is `PreToolUse` rules declared