fix(cli): retry transient connection errors in with_retry (#1132)

## Summary

`with_retry()` only retried exceptions when the error was an
`HTTPError`. Because of that, transient network errors like
`ConnectionError`, `ConnectTimeout`, and `urllib3` connection errors
were raised immediately, even though `_is_retriable()` already marks
them as retriable.

## Fix

Removed the extra `HTTPError` check and let `_is_retriable()` decide
whether an exception should be retried. This keeps the existing 429 /
`Retry-After` behavior the same while allowing transient connection
errors to retry as intended.

## Tests

Added tests to verify that:

- `ConnectionError` retries and succeeds
- `ConnectTimeout` retries and succeeds
- `urllib3.ProtocolError` retries and succeeds
- non-retriable exceptions still fail immediately

Existing `Retry-After` tests continue to pass.

Ran:

```bash
pytest tests/unit/test_retry_after.py