Add the mini XP display switch to PreferencesForm, wire it through the account page, and cover it in the integration test.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
- Fetch current user's leadOrActual preference in roster page via payload.auth()
- Add RosterDisplayContext to avoid prop drilling through org chart components
- MemberCard shows 'Lead' or 'Actual' based on user preference
- Add preference radio buttons to PreferencesForm under Display section
- Update updatePreferences server action to save leadOrActual
- Add TODO for restyling radio buttons later
