Temporary diagnostics to find why a deselected v4 exit node's synthesized
::/0 route still reaches the tunnel. Logs the full install path: incoming
client networks, route-selector state before/after the management-driven
update, what updateExitNodeSelections deselects/selects, and per-route
KEEP/SKIP/DROP decisions in FilterSelectedExitNodes and applyExitNodeFilter.
To be reverted once the real root cause is confirmed from a client log.