## Why
Exhausting the handshake failure budget closed the physical relay, disconnecting authenticated streams along with failed attempts.
## What changed
After eight failed handshakes, pause new handshake admission for 10 seconds. Reset incoming handshake attempts before parsing them while existing streams and pending validations continue. Failures during the cooldown do not extend it, and the failure budget resets when handshake admission resumes.
## Testing
Update relay tests to cover duplicate handshakes and early data without disconnecting the relay. Verify that encrypted traffic on an established stream continues during cooldown, rejected attempts skip authorization checks, and new handshakes succeed after cooldown expires.
GitOrigin-RevId: 0a5098ed1b3c31466f9c091f46cbb20415c7aa1d
105fe8761c