## Why
PR #28512 retries a failed session recovery every 100 ms. Every Noise
recovery attempt first asks the environment registry for a fresh
connection bundle, even when the eventual failure comes from the
WebSocket or initialize handshake. During an outage, that could make
each disconnected client call the registry about 250 times during the
25-second recovery window.
## What changes
All retryable Noise recovery failures now use a separate backoff
schedule:
```text
base: 500 ms -> 1 s -> 2 s -> 4 s -> 5 s maximum
actual: 500-750 ms, 1-1.5 s, 2-3 s, 4-6 s, 5-7.5 s
```
The extra 0-50% is deterministic per-session jitter so disconnected
clients do not retry together. Direct WebSocket recovery keeps the
existing 100 ms retry because it does not re-enter the registry.
jif