`terminal_hook` mapped `Restart` / `GracefulRestart` to `RevertIntent`, but
a restart never writes `wanted` — `restart_chain` deliberately has no
`SetWanted` head, so the tail `Reconcile` converges to the agent's existing
intent and a deliberately-stopped agent isn't forced up by a hive-wide
restart.
`revert_intent` writes `Wanted::from_running(observed)` unconditionally on a
cancelled DAG. So for an agent that is `wanted = Up` but currently down
(crashed, or caught behind another queued op), submitting a restart and then
cancelling it writes `wanted = Offline` — reverting an intent the DAG never
touched, to a value nobody asked for. Reconcile and crash-watch both then
read the agent as deliberately-stopped and leave it down.
It's invisible for a running agent, since `from_running(true)` equals the
intent already on file, which is why it went unnoticed. `cancel` only
succeeds while every node is still `Pending`, so the reachable window is
exactly "queued restart + observed != intent" — precisely when someone
restarts and then thinks better of it.
Drop both restart templates from the `RevertIntent` arm; they fall through
to no terminal hook, which is correct for a DAG that writes no intent.
Document the invariant on `HookKind::RevertIntent` and on `revert_intent`
itself: the hook writes *observed* state, so dispatching it for a template
with no `SetWanted` head doesn't restore an intent, it invents one.
Test covers all four restart shapes (graceful x running), asserting both
that the spec carries no `SetWanted` and that a cancelled restart dispatches
no hook, with a contrast arm pinning stop's revert in place.
Fixeshyperhive/hyperhive#2710
7589f4c06c