_search_employees always queried the external HR database (employee_connection),
so a site running the selfhosted employee directory (the app-owned
directoryemployees table) got zero employee results - searching an SSO or name
found nothing, and there was no way to reach the employee profile. Made it
mode-aware via the employee_directory_mode setting: selfhosted -> query the
DirectoryEmployee table (lazy, plugin-guarded); external -> the HR DB as before.
Verified: SSO 210009518 -> Jeff Pierce -> /employees/210009518; name "Pierce"
-> Pierce Cox, Andy Pierce, Jeff Pierce.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>