Function resolve_connection 

pub async fn resolve_connection(
    host: &str,
    port: Option<u16>,
    ws_url: Option<&str>,
) -> Result<ResolvedConnection, AppError>

Resolve a Chrome connection using the priority chain:

1. Explicit --ws-url
2. Explicit --port (user provided, not the default)
3. Session file (with health check)
4. Auto-discover (default host:port 9222)
5. Error with suggestion

Errors

Returns AppError if no Chrome connection can be resolved.