Closes #52943

## Summary
- Prefer SSH nicknames over raw hosts in remote connection display names
- Add regression tests for nickname and host fallback behavior

## Why
The `nickname` field is documented as the user-facing label for SSH
connections, but `RemoteConnectionOptions::display_name()` always
returned the raw host. That meant recent-projects UI surfaces kept
ignoring nicknames even when they were configured.

## Validation
- `cargo test -p remote ssh_display_name`
- `cargo test -p remote`

Release Notes:

- Fixed SSH recent-project labels to show configured nicknames instead
of raw hosts when available.