docs: add reconnection and error recovery docs

docs/USAGE.md

@@ -83,6 +83,21 @@ gain values.
 shown as warnings. Press `F5` again to confirm reconnect, or any
 other key to cancel.
 
+## Reconnection
+
+On unexpected disconnect (server restart, network loss), tuimble
+automatically retries with exponential backoff:
+
+- Initial delay: 2 seconds, doubling each attempt (2, 4, 8, 16, 30...)
+- Maximum delay: 30 seconds
+- Maximum attempts: 10
+
+The status bar shows `◐ reconnecting` during retry. If the server
+rejects authentication, retries stop immediately.
+
+After all attempts are exhausted, press `F5` to retry manually.
+`F5` also cancels an in-progress reconnect and starts a fresh attempt.
+
 ## Configuration
 
 See `~/.config/tuimble/config.toml`. All fields are optional;