rfc: client route liveness probing / reachability question

Author: snormore

rfcs/rfc7-client-route-liveness-probing.md

@@ -367,3 +367,4 @@ During the transition:
 - **Convergence Tuning** — What probe intervals and success/failure thresholds yield the best balance between responsiveness and stability across diverse network conditions?
 - **Visibility and Monitoring** — How can we detect and debug flapping or systemic probe loss across clients? Should aggregate telemetry on probe health be collected globally?
 - **ICMP Reachability Rollout** — Roughly 7% of clients do not currently respond to ICMP. What coverage level is acceptable before making probing the default behavior?
+- **Reachability Detection and Notification** — How will users discover when their client is not reachable via ICMP once probing becomes default-on? Should the CLI proactively test ICMP reachability during `connect` or `status` commands and surface an error or warning? Should the daemon detect and exit if not?