Pure rename, no behavior change: GeoAlertScreen -> LocatorScreen (file +
class), NodePrefs geo_alert_* fields -> locator_*, UITask engine functions
(evaluateGeoAlert/fireGeoAlert/geoAlertDistance/geoProximityBeeper) and state
-> evaluateLocator/fireLocator/locatorDistance/locatorProximityBeeper, Tools
menu entry and screen header text -> "Locator", plus matching docs/README
updates. NodePrefs field renames don't affect on-disk layout (DataStore
serializes by position, not name).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>