Three pieces, each verified on Android across WiFi/cellular switches:
- A sweep-aware backoff wrapper: the first retry after a disconnect
that follows a recent network-change mark comes after 200ms instead
of the randomized [0..1.6s] interval. Any other failure keeps the
unchanged spread, so the clients of a restarted server still scatter
their reconnects.
- The retry sleep wakes on OS network availability transitions
(nbgrpc.Retry): a disconnect that precedes the offline flag by a few
milliseconds no longer sleeps blindly through the recovery - the
loop parks on the netstate gate and resumes the moment the network
returns.
- The connection state is re-checked after WaitForStateChange: a dial
settling in Ready proceeds immediately instead of burning another
backoff round on an already-usable channel.
Measured after a network switch: management and signal recover in
270-470ms deterministically, down from a 312-1593ms lottery.
