Downloads killed by WiFi/mobile transitions failed with the generic
"Dictionary download failed" message because UnknownHostException,
ConnectException, unexpected end of stream, and closed-socket errors
were not classified as network errors and were never retried.
Classify them by exception type and message so the retry loop
engages and exhaustion reports the network-specific message.
Bump OkHttp 5.4.0 to 5.5.0: a throwing system proxy selector now
falls back to a direct connection instead of failing the call,
complementing the download resilience fix.
OneWay
bab03b6c73