Hour-long remote tasks were never delivered: a subscribe watch held one SSE stream for up to a day, the remote
sent nothing while its agent worked without text, and once the quiet connection died on the way (no FIN/RST) the
watch waited on it with no error and no log line.
- A subscription lasts at most 5 minutes (SubscriptionSlice), then GetTask and a new subscription: a pause, not a
failure. A slice ended mid-read counts as ours even when it surfaces as an I/O error.
- The shared handler connects with TCP keepalive (60 s, every 15 s, 4 probes) and HTTP/2 pings.
- Log lines when a watch starts or is restored, when a slice ends on a running task, when a result is delivered or
kept; the Telegram host's console log carries a UTC timestamp.
- action=status on a settled task ends its watch, so the result isn't delivered a second time.
- A "context busy" refusal of send says nothing was sent, names the watched task in that context and that its
result will arrive by itself; refusals never touch a watch.
