1. Handle op 7 (Server Reconnect): close WS to trigger reconnect loop
while preserving session for Resume
2. Handle op 9 (Invalid Session): check d value to determine if session
is resumable; clear session only when not resumable
3. Remove 4009 from session-clearing set (connection timeout is resumable)
4. Expand fatal close codes: 4001/4002/4010-4014 now stop reconnect
immediately instead of retrying uselessly
5. Add unit tests
walli
a54f5afc70