Whether proximity filter mode is currently active.
The custom circle overlay managed by proximity-circle.ts (null when inactive).
The custom centre-marker handle managed by proximity-circle.ts (null when inactive).
Reference to the active map instance (null when not yet initialised).
The map-click event handler registered during placement mode (null when inactive).
Pending radius value (metres) waiting to be applied after a marker placement.
Array of cleanup callbacks collected during proximity session (event listeners, etc.).
Internal runtime state shared by all proximity sub-modules. Tracks active map artefacts, modes, and cleanup callbacks.