fix(infra): Fix Docker Stats (9324) and PVE Exporter (9221) probe ports

Previously probed wrong ports:
- Docker Stats was at 9323 (dockerd metrics) but should be 9324
  (harness-docker-stats, docker_container_* metrics)
- PVE Exporter was at 9324 (harness-docker-stats) but should be 9221
  (harness-pve-exporter, 5 pve_* metrics)

Both exporters bind to 127.0.0.1 on CT 116 and must be probed via SSH.

Updated infrastructure-monitoring.prose.md to document the correct ports.
Added test assertions verifying the exact ports are probed.

Branch: fix/infra-monitoring-probe-ports-20260919

scripts/test_infra_monitoring.sh

@@ -121,12 +121,16 @@ assert "Port 9405 NOT in any curl call" \
     '! grep -q ":9405" "$CURL_LOG"'
 
 # ── 5. Docker Stats / PVE Exporter: SSH-probed at correct ports ────────────
-assert "Docker Stats probed at port 9323 via SSH" \
-    'grep -q "9323" "$SSH_LOG"'
-
-assert "PVE Exporter probed at port 9324 via SSH" \
+assert "Docker Stats probed at port 9324 via SSH" \
     'grep -q "9324" "$SSH_LOG"'
 
+assert "PVE Exporter probed at port 9221 via SSH" \
+    'grep -q "9221" "$SSH_LOG"'
+
+# ── 5a. Stale port 9323 (dockerd) NOT probed ──────────────────────────────
+assert "Port 9323 (dockerd) NOT in SSH log" \
+    '! grep -q "9323" "$SSH_LOG"'
+
 # ── 6. No stale ports in the script source (belt-and-suspenders) ──────────
 assert "Port 9325 (historical) NOT in script source" \
     '! grep -q "9325" "$SCRIPT"'