v0.0.19

Fix WMKS connection killed by premature ClientCaps and ACK messages

v0.0.18 sent ClientCaps with heartbeat bit to a server that doesn't support
heartbeat (0x021020bf has heartbeat=false), causing immediate connection close.
Also sent frame ACKs which may have been rejected.

Changes:
- Only send ClientCaps when server supports BOTH clientCaps AND heartbeat
- Remove frame ACK sending (v0.0.17 worked 36s without them)
- Add dead connection detection in reader goroutine (consecutive error tracking)
- Restore RFB message logging for debugging