fix(ipc): reset the state subscription's reconnect wait after a good connection (#740)

StateSubscription._run reset its backoff only when _follow() returned
normally, which happens only on stop(). Every real disconnect raises
ControlError, so the wait kept doubling across connections: after
successive display restarts the web resubscribed 1, 2, 4, 8, 16 and then
30 s later for good, answering from one-shot state.get connections in the
meantime. The docs promise "1 s up to 30 s" per outage.

The wait now goes back to the minimum once a connection got as far as
storing a snapshot, whatever ended it. A display without the stream
(unknown_command) is still retried at the slow interval.

The frozen-timestamp bug found in the same review is fixed by #737.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

src/ipc/client.py

@@ -396,9 +396,9 @@ class StateSubscription:
     def _run(self) -> None:
         backoff = _RECONNECT_MIN_SECONDS
         while not self._stop.is_set():
+            snapshots = self.snapshots
             try:
                 self._follow()
-                backoff = _RECONNECT_MIN_SECONDS
             except ControlError as e:
                 self.last_error = e.reason
                 if e.reason in _SLOW_RETRY_REASONS:
@@ -414,6 +414,11 @@ class StateSubscription:
                         sock.close()
                     except OSError:
                         pass
+            if self.snapshots != snapshots:
+                # This connection got as far as the display's state: whatever
+                # ended it (a restart, most often), it was working, so the
+                # next try starts from the shortest wait again.
+                backoff = _RECONNECT_MIN_SECONDS
             if self._stop.wait(backoff):
                 return
             backoff = min(backoff * 2, _RECONNECT_MAX_SECONDS)