AP-role metrics: client telemetry replaces dead STA/campground metrics

- metrics.lua: drop vif-sta0 station + campground-gateway sections (roof
  is a dumb AP since 2026-06-07); add skyweave_ap_* families — client
  count, per-client signal/SNR/bitrates/idle/association-time from
  iwinfo assoclist, noise floor, txpower, channel. Ping targets now
  chateau_gateway + talos_via_tunnel + internet (DNS).
- skyweave-push.sh: PUT instead of POST so departed-client series and
  retired families don't linger on the pushgateway; skip push when the
  local metrics fetch fails.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

skyweave-push.sh

@@ -1,9 +1,15 @@
 #!/bin/sh
 # Push skyweave metrics to Prometheus pushgateway every 30 seconds.
+# PUT (not POST) so the whole group is replaced each cycle — per-client
+# series for departed stations don't linger. Skips the push if the local
+# metrics fetch fails, so a CGI hiccup never blanks the group.
 PUSHGW="http://192.168.88.44:9091/metrics/job/rvlink/instance/rvlink"
 METRICS_URL="http://127.0.0.1:42069/cgi-bin/skyweave.lua/metrics"
 
 while true; do
-    curl -sf "$METRICS_URL" | curl -sf --data-binary @- "$PUSHGW" >/dev/null 2>&1
+    BODY=$(curl -sf "$METRICS_URL")
+    if [ -n "$BODY" ]; then
+        printf '%s\n' "$BODY" | curl -sf -X PUT --data-binary @- "$PUSHGW" >/dev/null 2>&1
+    fi
     sleep 30
 done