## Why
Failed cloud discovery previously retried before each model step. Apply a cooldown across steps and turns to avoid repeated discovery requests while a provider remains unavailable.
## What changed
- Share per-thread retry backoff logic between cloud skill and plugin catalogs, starting at 30 seconds and doubling to a maximum of 5 minutes.
- Scope cooldowns to authentication and MCP resource generations so account changes and reconnects permit immediate recovery.
- Clear backoff after successful discovery or configuration resets, while allowing cancelled refreshes to retry immediately.
## Testing
Update lifecycle and concurrency tests to cover shared cooldowns, reconnect recovery, and cancellation. Use paused time to verify exponential delays, the 5-minute cap, and backoff across turns.
GitOrigin-RevId: 30dab5ceba51e8ad64c0794c1729719e99f577ce
